diff --git a/packages/@ember/-internals/glimmer/lib/helpers/-normalize-class.ts b/packages/@ember/-internals/glimmer/lib/helpers/-normalize-class.ts
index 52b2989294b..5603e12c135 100644
--- a/packages/@ember/-internals/glimmer/lib/helpers/-normalize-class.ts
+++ b/packages/@ember/-internals/glimmer/lib/helpers/-normalize-class.ts
@@ -1,5 +1,5 @@
 import { assert } from '@ember/debug';
-import { dasherize } from '@ember/string';
+import { dasherize } from '@ember/-internals/string';
 import type { CapturedArguments } from '@glimmer/interfaces';
 import { createComputeRef, valueForRef } from '@glimmer/reference';
 import { internalHelper } from './internal-helper';
diff --git a/packages/@ember/-internals/glimmer/lib/utils/bindings.ts b/packages/@ember/-internals/glimmer/lib/utils/bindings.ts
index 26069564072..aa04023b570 100644
--- a/packages/@ember/-internals/glimmer/lib/utils/bindings.ts
+++ b/packages/@ember/-internals/glimmer/lib/utils/bindings.ts
@@ -1,6 +1,6 @@
 import { get } from '@ember/-internals/metal';
 import { assert } from '@ember/debug';
-import { dasherize } from '@ember/string';
+import { dasherize } from '@ember/-internals/string';
 import type { ElementOperations } from '@glimmer/interfaces';
 import type { Reference } from '@glimmer/reference';
 import {
diff --git a/packages/@ember/-internals/string/index.ts b/packages/@ember/-internals/string/index.ts
new file mode 100644
index 00000000000..e2e2591b6b4
--- /dev/null
+++ b/packages/@ember/-internals/string/index.ts
@@ -0,0 +1,105 @@
+/*
+  This module exists to separate the @ember/string methods used
+  internally in ember-source, from those public methods that are
+  now deprecated and to be removed.
+*/
+
+import { Cache } from '@ember/-internals/utils';
+
+const STRING_DASHERIZE_REGEXP = /[ _]/g;
+
+const STRING_DASHERIZE_CACHE = new Cache<string, string>(1000, (key) =>
+  decamelize(key).replace(STRING_DASHERIZE_REGEXP, '-')
+);
+
+const STRING_CLASSIFY_REGEXP_1 = /^(-|_)+(.)?/;
+const STRING_CLASSIFY_REGEXP_2 = /(.)(-|_|\.|\s)+(.)?/g;
+const STRING_CLASSIFY_REGEXP_3 = /(^|\/|\.)([a-z])/g;
+
+const CLASSIFY_CACHE = new Cache<string, string>(1000, (str) => {
+  let replace1 = (_match: string, _separator: string, chr: string) =>
+    chr ? `_${chr.toUpperCase()}` : '';
+  let replace2 = (_match: string, initialChar: string, _separator: string, chr: string) =>
+    initialChar + (chr ? chr.toUpperCase() : '');
+  let parts = str.split('/');
+  for (let i = 0; i < parts.length; i++) {
+    parts[i] = parts[i]!.replace(STRING_CLASSIFY_REGEXP_1, replace1).replace(
+      STRING_CLASSIFY_REGEXP_2,
+      replace2
+    );
+  }
+  return parts
+    .join('/')
+    .replace(STRING_CLASSIFY_REGEXP_3, (match /*, separator, chr */) => match.toUpperCase());
+});
+
+const STRING_DECAMELIZE_REGEXP = /([a-z\d])([A-Z])/g;
+
+const DECAMELIZE_CACHE = new Cache<string, string>(1000, (str) =>
+  str.replace(STRING_DECAMELIZE_REGEXP, '$1_$2').toLowerCase()
+);
+
+/**
+ Defines string helper methods used internally in ember-source.
+
+ @class String
+ @private
+ */
+
+/**
+ Replaces underscores, spaces, or camelCase with dashes.
+
+ ```javascript
+ import { dasherize } from '@ember/-internals/string';
+
+ dasherize('innerHTML');                // 'inner-html'
+ dasherize('action_name');              // 'action-name'
+ dasherize('css-class-name');           // 'css-class-name'
+ dasherize('my favorite items');        // 'my-favorite-items'
+ dasherize('privateDocs/ownerInvoice';  // 'private-docs/owner-invoice'
+ ```
+
+ @method dasherize
+ @param {String} str The string to dasherize.
+ @return {String} the dasherized string.
+ @private
+ */
+export function dasherize(str: string): string {
+  return STRING_DASHERIZE_CACHE.get(str);
+}
+
+/**
+ Returns the UpperCamelCase form of a string.
+
+ ```javascript
+ import { classify } from '@ember/string';
+
+ classify('innerHTML');                   // 'InnerHTML'
+ classify('action_name');                 // 'ActionName'
+ classify('css-class-name');              // 'CssClassName'
+ classify('my favorite items');           // 'MyFavoriteItems'
+ classify('private-docs/owner-invoice');  // 'PrivateDocs/OwnerInvoice'
+ ```
+
+ @method classify
+ @param {String} str the string to classify
+ @return {String} the classified string
+ @private
+ */
+export function classify(str: string): string {
+  return CLASSIFY_CACHE.get(str);
+}
+
+/**
+ Converts a camelized string into all lower case separated by underscores.
+
+ ```javascript
+ decamelize('innerHTML');          // 'inner_html'
+ decamelize('action_name');        // 'action_name'
+ decamelize('css-class-name');     // 'css-class-name'
+ decamelize('my favorite items');  // 'my favorite items'
+ ```
+ */
+function decamelize(str: string): string {
+  return DECAMELIZE_CACHE.get(str);
+}
diff --git a/packages/@ember/-internals/string/tests/classify_test.js b/packages/@ember/-internals/string/tests/classify_test.js
new file mode 100644
index 00000000000..a167dbfcbcb
--- /dev/null
+++ b/packages/@ember/-internals/string/tests/classify_test.js
@@ -0,0 +1,65 @@
+/* eslint-disable qunit/no-test-expect-argument */
+import { classify } from '@ember/-internals/string';
+import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
+
+function test(assert, given, expected, description) {
+  assert.deepEqual(classify(given), expected, description);
+}
+
+moduleFor(
+  'EmberInternalsString.classify',
+  class extends AbstractTestCase {
+    ['@test String classify tests'](assert) {
+      test(assert, 'my favorite items', 'MyFavoriteItems', 'classify normal string');
+      test(assert, 'css-class-name', 'CssClassName', 'classify dasherized string');
+      test(assert, 'action_name', 'ActionName', 'classify underscored string');
+      test(
+        assert,
+        'privateDocs/ownerInvoice',
+        'PrivateDocs/OwnerInvoice',
+        'classify namespaced camelized string'
+      );
+      test(
+        assert,
+        'private_docs/owner_invoice',
+        'PrivateDocs/OwnerInvoice',
+        'classify namespaced underscored string'
+      );
+      test(
+        assert,
+        'private-docs/owner-invoice',
+        'PrivateDocs/OwnerInvoice',
+        'classify namespaced dasherized string'
+      );
+      test(assert, '-view-registry', '_ViewRegistry', 'classify prefixed dasherized string');
+      test(
+        assert,
+        'components/-text-field',
+        'Components/_TextField',
+        'classify namespaced prefixed dasherized string'
+      );
+      test(assert, '_Foo_Bar', '_FooBar', 'classify underscore-prefixed underscored string');
+      test(assert, '_Foo-Bar', '_FooBar', 'classify underscore-prefixed dasherized string');
+      test(
+        assert,
+        '_foo/_bar',
+        '_Foo/_Bar',
+        'classify underscore-prefixed-namespaced underscore-prefixed string'
+      );
+      test(
+        assert,
+        '-foo/_bar',
+        '_Foo/_Bar',
+        'classify dash-prefixed-namespaced underscore-prefixed string'
+      );
+      test(
+        assert,
+        '-foo/-bar',
+        '_Foo/_Bar',
+        'classify dash-prefixed-namespaced dash-prefixed string'
+      );
+      test(assert, 'InnerHTML', 'InnerHTML', 'does nothing with classified string');
+      test(assert, '_FooBar', '_FooBar', 'does nothing with classified prefixed string');
+    }
+  }
+);
diff --git a/packages/@ember/-internals/string/tests/dasherize_test.js b/packages/@ember/-internals/string/tests/dasherize_test.js
new file mode 100644
index 00000000000..090cb1b429d
--- /dev/null
+++ b/packages/@ember/-internals/string/tests/dasherize_test.js
@@ -0,0 +1,43 @@
+/* eslint-disable qunit/no-test-expect-argument */
+import { dasherize } from '@ember/-internals/string';
+import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
+
+function test(assert, given, expected, description) {
+  assert.deepEqual(dasherize(given), expected, description);
+}
+
+moduleFor(
+  'EmberInternalsString.dasherize',
+  class extends AbstractTestCase {
+    ['@test String dasherize tests'](assert) {
+      test(assert, 'my favorite items', 'my-favorite-items', 'dasherize normal string');
+      test(assert, 'css-class-name', 'css-class-name', 'does nothing with dasherized string');
+      test(assert, 'action_name', 'action-name', 'dasherize underscored string');
+      test(assert, 'innerHTML', 'inner-html', 'dasherize camelcased string');
+      test(
+        assert,
+        'toString',
+        'to-string',
+        'dasherize string that is the property name of Object.prototype'
+      );
+      test(
+        assert,
+        'PrivateDocs/OwnerInvoice',
+        'private-docs/owner-invoice',
+        'dasherize namespaced classified string'
+      );
+      test(
+        assert,
+        'privateDocs/ownerInvoice',
+        'private-docs/owner-invoice',
+        'dasherize namespaced camelized string'
+      );
+      test(
+        assert,
+        'private_docs/owner_invoice',
+        'private-docs/owner-invoice',
+        'dasherize namespaced underscored string'
+      );
+    }
+  }
+);
diff --git a/packages/@ember/debug/container-debug-adapter.ts b/packages/@ember/debug/container-debug-adapter.ts
index 43e490de888..2a6617548b4 100644
--- a/packages/@ember/debug/container-debug-adapter.ts
+++ b/packages/@ember/debug/container-debug-adapter.ts
@@ -1,4 +1,4 @@
-import { classify, dasherize } from '@ember/string';
+import { classify, dasherize } from '@ember/-internals/string';
 import EmberObject from '@ember/object';
 import { typeOf } from '@ember/utils';
 import type { InternalOwner } from '@ember/-internals/owner';
diff --git a/packages/@ember/debug/data-adapter.ts b/packages/@ember/debug/data-adapter.ts
index bc02dc4b5c9..056b69748c8 100644
--- a/packages/@ember/debug/data-adapter.ts
+++ b/packages/@ember/debug/data-adapter.ts
@@ -2,7 +2,7 @@ import type { InternalOwner } from '@ember/-internals/owner';
 import { getOwner } from '@ember/-internals/owner';
 import { _backburner, next } from '@ember/runloop';
 import { get } from '@ember/object';
-import { dasherize } from '@ember/string';
+import { dasherize } from '@ember/-internals/string';
 import Namespace from '@ember/application/namespace';
 import type { NativeArray } from '@ember/array';
 import EmberObject from '@ember/object';
diff --git a/packages/@ember/object/tests/observable_test.js b/packages/@ember/object/tests/observable_test.js
index a000ec06e9e..c23f55dd650 100644
--- a/packages/@ember/object/tests/observable_test.js
+++ b/packages/@ember/object/tests/observable_test.js
@@ -1,7 +1,6 @@
 import { context } from '@ember/-internals/environment';
 import { run } from '@ember/runloop';
 import { get, computed } from '@ember/object';
-import { w } from '@ember/string';
 import EmberObject, { observer } from '@ember/object';
 import Observable from '@ember/object/observable';
 import { A as emberA } from '@ember/array';
@@ -359,7 +358,7 @@ moduleFor(
 
     ['@test getting values should call function return value'](assert) {
       // get each property twice. Verify return.
-      let keys = w('computed dependent');
+      let keys = ['computed', 'dependent'];
 
       keys.forEach(function (key) {
         assert.equal(object.get(key), key, `Try #1: object.get(${key}) should run function`);
@@ -367,15 +366,15 @@ moduleFor(
       });
 
       // verify each call count. cached should only be called once
-      w('computedCalls dependentCalls').forEach((key) => {
+      ['computedCalls', 'dependentCalls'].forEach((key) => {
         assert.equal(object[key].length, 1, `non-cached property ${key} should be called 1x`);
       });
     }
 
     ['@test setting values should call function return value'](assert) {
       // get each property twice. Verify return.
-      let keys = w('computed dependent');
-      let values = w('value1 value2');
+      let keys = ['computed', 'dependent'];
+      let values = ['value1', 'value2'];
 
       keys.forEach((key) => {
         assert.equal(
diff --git a/packages/@ember/string/index.ts b/packages/@ember/string/index.ts
index d96d1604eae..7f845c66a95 100644
--- a/packages/@ember/string/index.ts
+++ b/packages/@ember/string/index.ts
@@ -76,6 +76,7 @@ const DECAMELIZE_CACHE = new Cache<string, string>(1000, (str) =>
 
   @class String
   @public
+  @deprecated Add the package `@ember/string` to your project to use in place of this module.
 */
 
 /**
@@ -98,8 +99,10 @@ const DECAMELIZE_CACHE = new Cache<string, string>(1000, (str) =>
   @param {String} str The string to split
   @return {Array} array containing the split strings
   @public
+  @deprecated Add `@ember/string` to your package.json
 */
 export function w(str: string): string[] {
+  deprecateImportFromInternalString();
   return str.split(/\s+/);
 }
 
@@ -119,8 +122,10 @@ export function w(str: string): string[] {
   @param {String} str The string to decamelize.
   @return {String} the decamelized string.
   @public
+  @deprecated Add `@ember/string` to your package.json
 */
 export function decamelize(str: string): string {
+  deprecateImportFromInternalString();
   return DECAMELIZE_CACHE.get(str);
 }
 
@@ -141,8 +146,10 @@ export function decamelize(str: string): string {
   @param {String} str The string to dasherize.
   @return {String} the dasherized string.
   @public
+  @deprecated Add `@ember/string` to your package.json
 */
 export function dasherize(str: string): string {
+  deprecateImportFromInternalString();
   return STRING_DASHERIZE_CACHE.get(str);
 }
 
@@ -164,8 +171,10 @@ export function dasherize(str: string): string {
   @param {String} str The string to camelize.
   @return {String} the camelized string.
   @public
+  @deprecated Add `@ember/string` to your package.json
 */
 export function camelize(str: string): string {
+  deprecateImportFromInternalString();
   return CAMELIZE_CACHE.get(str);
 }
 
@@ -186,8 +195,10 @@ export function camelize(str: string): string {
   @param {String} str the string to classify
   @return {String} the classified string
   @public
+  @deprecated Add `@ember/string` to your package.json
 */
 export function classify(str: string): string {
+  deprecateImportFromInternalString();
   return CLASSIFY_CACHE.get(str);
 }
 
@@ -209,8 +220,10 @@ export function classify(str: string): string {
   @param {String} str The string to underscore.
   @return {String} the underscored string.
   @public
+  @deprecated Add `@ember/string` to your package.json
 */
 export function underscore(str: string): string {
+  deprecateImportFromInternalString();
   return UNDERSCORE_CACHE.get(str);
 }
 
@@ -231,11 +244,30 @@ export function underscore(str: string): string {
   @param {String} str The string to capitalize.
   @return {String} The capitalized string.
   @public
+  @deprecated Add `@ember/string` to your package.json
 */
 export function capitalize(str: string): string {
+  deprecateImportFromInternalString();
   return CAPITALIZE_CACHE.get(str);
 }
 
+function deprecateImportFromInternalString() {
+  deprecate(
+    'Importing from `@ember/string` without having the `@ember/string` package in your project is deprecated. Please add `@ember/string` to your `package.json',
+    false,
+    {
+      id: 'ember-string.add-package',
+      for: 'ember-source',
+      since: {
+        available: '4.10',
+        enabled: '4.10',
+      },
+      until: '5.0.0',
+      url: 'https://deprecations.emberjs.com/v4.x/#toc_ember-string-add-package',
+    }
+  );
+}
+
 function deprecateImportFromString(
   name: string,
   message = `Importing ${name} from '@ember/string' is deprecated. Please import ${name} from '@ember/template' instead.`
diff --git a/packages/@ember/string/tests/camelize_test.js b/packages/@ember/string/tests/camelize_test.js
index 1cb053fa798..c579be15ead 100644
--- a/packages/@ember/string/tests/camelize_test.js
+++ b/packages/@ember/string/tests/camelize_test.js
@@ -3,7 +3,9 @@ import { camelize } from '@ember/string';
 import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
 
 function test(assert, given, expected, description) {
-  assert.deepEqual(camelize(given), expected, description);
+  expectDeprecation(() => {
+    assert.deepEqual(camelize(given), expected, description);
+  }, 'Importing from `@ember/string` without having the `@ember/string` package in your project is deprecated. Please add `@ember/string` to your `package.json');
 }
 
 moduleFor(
diff --git a/packages/@ember/string/tests/capitalize_test.js b/packages/@ember/string/tests/capitalize_test.js
index 7b11679722a..4fc1e757bc4 100644
--- a/packages/@ember/string/tests/capitalize_test.js
+++ b/packages/@ember/string/tests/capitalize_test.js
@@ -3,7 +3,9 @@ import { capitalize } from '@ember/string';
 import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
 
 function test(assert, given, expected, description) {
-  assert.deepEqual(capitalize(given), expected, description);
+  expectDeprecation(() => {
+    assert.deepEqual(capitalize(given), expected, description);
+  }, 'Importing from `@ember/string` without having the `@ember/string` package in your project is deprecated. Please add `@ember/string` to your `package.json');
 }
 
 moduleFor(
diff --git a/packages/@ember/string/tests/classify_test.js b/packages/@ember/string/tests/classify_test.js
index 5232ccbf8c5..13dca64b245 100644
--- a/packages/@ember/string/tests/classify_test.js
+++ b/packages/@ember/string/tests/classify_test.js
@@ -3,7 +3,9 @@ import { classify } from '@ember/string';
 import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
 
 function test(assert, given, expected, description) {
-  assert.deepEqual(classify(given), expected, description);
+  expectDeprecation(() => {
+    assert.deepEqual(classify(given), expected, description);
+  }, 'Importing from `@ember/string` without having the `@ember/string` package in your project is deprecated. Please add `@ember/string` to your `package.json');
 }
 
 moduleFor(
diff --git a/packages/@ember/string/tests/dasherize_test.js b/packages/@ember/string/tests/dasherize_test.js
index 9f41db6957b..98fb5a5dcf1 100644
--- a/packages/@ember/string/tests/dasherize_test.js
+++ b/packages/@ember/string/tests/dasherize_test.js
@@ -3,7 +3,9 @@ import { dasherize } from '@ember/string';
 import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
 
 function test(assert, given, expected, description) {
-  assert.deepEqual(dasherize(given), expected, description);
+  expectDeprecation(() => {
+    assert.deepEqual(dasherize(given), expected, description);
+  }, 'Importing from `@ember/string` without having the `@ember/string` package in your project is deprecated. Please add `@ember/string` to your `package.json');
 }
 
 moduleFor(
diff --git a/packages/@ember/string/tests/decamelize_test.js b/packages/@ember/string/tests/decamelize_test.js
index f37af0c66a2..d5620398cd1 100644
--- a/packages/@ember/string/tests/decamelize_test.js
+++ b/packages/@ember/string/tests/decamelize_test.js
@@ -3,7 +3,9 @@ import { decamelize } from '@ember/string';
 import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
 
 function test(assert, given, expected, description) {
-  assert.deepEqual(decamelize(given), expected, description);
+  expectDeprecation(() => {
+    assert.deepEqual(decamelize(given), expected, description);
+  }, 'Importing from `@ember/string` without having the `@ember/string` package in your project is deprecated. Please add `@ember/string` to your `package.json');
 }
 
 moduleFor(
diff --git a/packages/@ember/string/tests/underscore_test.js b/packages/@ember/string/tests/underscore_test.js
index 69a1b83b33b..11ea62ab652 100644
--- a/packages/@ember/string/tests/underscore_test.js
+++ b/packages/@ember/string/tests/underscore_test.js
@@ -3,7 +3,9 @@ import { underscore } from '@ember/string';
 import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
 
 function test(assert, given, expected, description) {
-  assert.deepEqual(underscore(given), expected, description);
+  expectDeprecation(() => {
+    assert.deepEqual(underscore(given), expected, description);
+  }, 'Importing from `@ember/string` without having the `@ember/string` package in your project is deprecated. Please add `@ember/string` to your `package.json');
 }
 
 moduleFor(
diff --git a/packages/@ember/string/tests/w_test.js b/packages/@ember/string/tests/w_test.js
index e9fada90f2a..ae5dc9912bd 100644
--- a/packages/@ember/string/tests/w_test.js
+++ b/packages/@ember/string/tests/w_test.js
@@ -3,7 +3,9 @@ import { w } from '@ember/string';
 import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
 
 function test(assert, given, expected, description) {
-  assert.deepEqual(w(given), expected, description);
+  expectDeprecation(() => {
+    assert.deepEqual(w(given), expected, description);
+  }, 'Importing from `@ember/string` without having the `@ember/string` package in your project is deprecated. Please add `@ember/string` to your `package.json');
 }
 
 moduleFor(
diff --git a/packages/ember/tests/routing/query_params_test.js b/packages/ember/tests/routing/query_params_test.js
index 618e4a4b6e4..3d213fcac5e 100644
--- a/packages/ember/tests/routing/query_params_test.js
+++ b/packages/ember/tests/routing/query_params_test.js
@@ -1,5 +1,5 @@
 import Controller from '@ember/controller';
-import { dasherize } from '@ember/string';
+import { dasherize } from '@ember/-internals/string';
 import EmberObject, { get, computed } from '@ember/object';
 import { RSVP } from '@ember/-internals/runtime';
 import { A as emberA } from '@ember/array';
diff --git a/packages/ember/tests/routing/router_service_test/urlFor_test.js b/packages/ember/tests/routing/router_service_test/urlFor_test.js
index 8b091812e58..486709c2c5b 100644
--- a/packages/ember/tests/routing/router_service_test/urlFor_test.js
+++ b/packages/ember/tests/routing/router_service_test/urlFor_test.js
@@ -1,11 +1,10 @@
 import Controller from '@ember/controller';
-import { capitalize } from '@ember/string';
 import Route from '@ember/routing/route';
 import { get } from '@ember/object';
 import { RouterTestCase, moduleFor } from 'internal-test-helpers';
 
 function setupController(app, name) {
-  let controllerName = `${capitalize(name)}Controller`;
+  let controllerName = `${name}Controller`;
 
   Object.defineProperty(app, controllerName, {
     get() {
@@ -30,7 +29,7 @@ moduleFor(
     ['@test RouterService#urlFor returns URL for simple route with dynamic segments'](assert) {
       assert.expect(1);
 
-      setupController(this.application, 'dynamic');
+      setupController(this.application, 'Dynamic');
 
       let dynamicModel = { id: 1, contents: 'much dynamicism' };