diff --git a/browser/components/preferences/dialogs/browserLanguages.js b/browser/components/preferences/dialogs/browserLanguages.js
index cf1bfd4407862..880e332c7c1fe 100644
--- a/browser/components/preferences/dialogs/browserLanguages.js
+++ b/browser/components/preferences/dialogs/browserLanguages.js
@@ -360,10 +360,10 @@ function compareItems(a, b) {
 }
 
 var gBrowserLanguagesDialog = {
-  telemetryId: null,
+  _telemetryId: null,
   accepted: false,
-  _availableLocales: null,
-  _selectedLocales: null,
+  _availableLocalesUI: null,
+  _selectedLocalesUI: null,
   selectedLocales: null,
 
   get downloadEnabled() {
@@ -376,7 +376,7 @@ var gBrowserLanguagesDialog = {
       "intl.ui.browserLanguage",
       method,
       "dialog",
-      this.telemetryId,
+      this._telemetryId,
       extra
     );
   },
@@ -392,7 +392,7 @@ var gBrowserLanguagesDialog = {
       .addEventListener("beforeaccept", () => this.beforeAccept());
     // Maintain the previously selected locales even if we cancel out.
     let { telemetryId, selected, search } = window.arguments[0];
-    this.telemetryId = telemetryId;
+    this._telemetryId = telemetryId;
     this.selectedLocales = selected;
 
     // This is a list of available locales that the user selected. It's more
@@ -420,7 +420,7 @@ var gBrowserLanguagesDialog = {
   },
 
   async initSelectedLocales(selectedLocales) {
-    this._selectedLocales = new OrderedListBox({
+    this._selectedLocalesUI = new OrderedListBox({
       richlistbox: document.getElementById("selectedLocales"),
       upButton: document.getElementById("up"),
       downButton: document.getElementById("down"),
@@ -428,11 +428,13 @@ var gBrowserLanguagesDialog = {
       onRemove: item => this.selectedLocaleRemoved(item),
       onReorder: () => this.recordTelemetry("reorder"),
     });
-    this._selectedLocales.setItems(await getLocaleDisplayInfo(selectedLocales));
+    this._selectedLocalesUI.setItems(
+      await getLocaleDisplayInfo(selectedLocales)
+    );
   },
 
   async initAvailableLocales(available, search) {
-    this._availableLocales = new SortedItemSelectList({
+    this._availableLocalesUI = new SortedItemSelectList({
       menulist: document.getElementById("availableLocales"),
       button: document.getElementById("add"),
       compareFn: compareItems,
@@ -467,7 +469,9 @@ var gBrowserLanguagesDialog = {
     }
 
     // Disable the dropdown while we hit the network.
-    this._availableLocales.disableWithMessageId("browser-languages-searching");
+    this._availableLocalesUI.disableWithMessageId(
+      "browser-languages-searching"
+    );
 
     // Fetch the available langpacks from AMO.
     let availableLangpacks;
@@ -502,13 +506,13 @@ var gBrowserLanguagesDialog = {
     });
 
     // Remove the search option and add the remote locales.
-    let items = this._availableLocales.items;
+    let items = this._availableLocalesUI.items;
     items.pop();
     items = items.concat(availableItems);
 
     // Update the dropdown and enable it again.
-    this._availableLocales.setItems(items);
-    this._availableLocales.enableWithMessageId(
+    this._availableLocalesUI.setItems(items);
+    this._availableLocalesUI.enableWithMessageId(
       "browser-languages-select-language"
     );
   },
@@ -527,7 +531,7 @@ var gBrowserLanguagesDialog = {
         value: "search",
       });
     }
-    this._availableLocales.setItems(items);
+    this._availableLocalesUI.setItems(items);
   },
 
   async availableLanguageSelected(item) {
@@ -543,22 +547,22 @@ var gBrowserLanguagesDialog = {
   },
 
   async requestLocalLanguage(item, available) {
-    this._selectedLocales.addItem(item);
-    let selectedCount = this._selectedLocales.items.length;
+    this._selectedLocalesUI.addItem(item);
+    let selectedCount = this._selectedLocalesUI.items.length;
     let availableCount = (await getAvailableLocales()).length;
     if (selectedCount == availableCount) {
       // Remove the installed label, they're all installed.
-      this._availableLocales.items.shift();
-      this._availableLocales.setItems(this._availableLocales.items);
+      this._availableLocalesUI.items.shift();
+      this._availableLocalesUI.setItems(this._availableLocalesUI.items);
     }
     // The label isn't always reset when the selected item is removed, so set it again.
-    this._availableLocales.enableWithMessageId(
+    this._availableLocalesUI.enableWithMessageId(
       "browser-languages-select-language"
     );
   },
 
   async requestRemoteLanguage(item) {
-    this._availableLocales.disableWithMessageId(
+    this._availableLocalesUI.disableWithMessageId(
       "browser-languages-downloading"
     );
 
@@ -580,8 +584,8 @@ var gBrowserLanguagesDialog = {
     }
 
     item.installed = true;
-    this._selectedLocales.addItem(item);
-    this._availableLocales.enableWithMessageId(
+    this._selectedLocalesUI.addItem(item);
+    this._availableLocalesUI.enableWithMessageId(
       "browser-languages-select-language"
     );
 
@@ -605,7 +609,7 @@ var gBrowserLanguagesDialog = {
 
   showError() {
     document.getElementById("warning-message").hidden = false;
-    this._availableLocales.enableWithMessageId(
+    this._availableLocalesUI.enableWithMessageId(
       "browser-languages-select-language"
     );
 
@@ -624,17 +628,17 @@ var gBrowserLanguagesDialog = {
   },
 
   getSelectedLocales() {
-    return this._selectedLocales.items.map(item => item.value);
+    return this._selectedLocalesUI.items.map(item => item.value);
   },
 
   async selectedLocaleRemoved(item) {
     this.recordTelemetry("remove");
 
-    this._availableLocales.addItem(item);
+    this._availableLocalesUI.addItem(item);
 
     // If the item we added is at the top of the list, it needs the label.
-    if (this._availableLocales.items[0] == item) {
-      this._availableLocales.addItem(await this.createInstalledLabel());
+    if (this._availableLocalesUI.items[0] == item) {
+      this._availableLocalesUI.addItem(await this.createInstalledLabel());
     }
   },
 
diff --git a/browser/components/preferences/main.inc.xhtml b/browser/components/preferences/main.inc.xhtml
index c537a22888d42..406bae47c6b44 100644
--- a/browser/components/preferences/main.inc.xhtml
+++ b/browser/components/preferences/main.inc.xhtml
@@ -277,7 +277,7 @@
   <vbox id="browserLanguagesBox" align="start" hidden="true">
     <description flex="1" controls="chooseBrowserLanguage" data-l10n-id="choose-browser-language-description"/>
     <hbox>
-      <menulist id="defaultBrowserLanguage">
+      <menulist id="primaryBrowserLocale">
         <menupopup/>
       </menulist>
       <button id="manageBrowserLanguagesButton"
diff --git a/browser/components/preferences/main.js b/browser/components/preferences/main.js
index a39efb5d772aa..257b2a245271f 100644
--- a/browser/components/preferences/main.js
+++ b/browser/components/preferences/main.js
@@ -328,7 +328,7 @@ var gMainPane = {
     initializeProxyUI(gMainPane);
 
     if (Services.prefs.getBoolPref("intl.multilingual.enabled")) {
-      gMainPane.initBrowserLocale();
+      gMainPane.initPrimaryBrowserLanguageUI();
     }
 
     // We call `initDefaultZoomValues` to set and unhide the
@@ -396,7 +396,7 @@ var gMainPane = {
       Services.prefs.clearUserPref("browser.ctrlTab.migrated");
     });
     setEventListener("manageBrowserLanguagesButton", "command", function() {
-      gMainPane.showBrowserLanguages({ search: false });
+      gMainPane.showBrowserLanguagesSubDialog({ search: false });
     });
     if (AppConstants.MOZ_UPDATER) {
       // These elements are only compiled in when the updater is enabled
@@ -986,7 +986,7 @@ var gMainPane = {
     document.getElementById("zoomBox").hidden = false;
   },
 
-  initBrowserLocale() {
+  initPrimaryBrowserLanguageUI() {
     // Enable telemetry.
     Services.telemetry.setEventRecordingEnabled(
       "intl.ui.browserLanguage",
@@ -994,12 +994,12 @@ var gMainPane = {
     );
 
     // This will register the "command" listener.
-    let menulist = document.getElementById("defaultBrowserLanguage");
+    let menulist = document.getElementById("primaryBrowserLocale");
     new SelectionChangedMenulist(menulist, event => {
-      gMainPane.onBrowserLanguageChange(event);
+      gMainPane.onPrimaryBrowserLanguageMenuChange(event);
     });
 
-    gMainPane.setBrowserLocales(Services.locale.appLocaleAsBCP47);
+    gMainPane.updatePrimaryBrowserLanguageUI(Services.locale.appLocaleAsBCP47);
   },
 
   /**
@@ -1007,7 +1007,7 @@ var gMainPane = {
    * is "selecting". This could be the currently requested locale or a locale
    * that the user would like to switch to after confirmation.
    */
-  async setBrowserLocales(selected) {
+  async updatePrimaryBrowserLanguageUI(selected) {
     let available = await getAvailableLocales();
     let localeNames = Services.intl.getLocaleDisplayNames(
       undefined,
@@ -1028,7 +1028,7 @@ var gMainPane = {
     // Add an option to search for more languages if downloading is supported.
     if (Services.prefs.getBoolPref("intl.multilingual.downloadEnabled")) {
       let menuitem = document.createXULElement("menuitem");
-      menuitem.id = "defaultBrowserLanguageSearch";
+      menuitem.id = "primaryBrowserLocaleSearch";
       menuitem.setAttribute(
         "label",
         await document.l10n.formatValue("browser-languages-search")
@@ -1037,7 +1037,7 @@ var gMainPane = {
       fragment.appendChild(menuitem);
     }
 
-    let menulist = document.getElementById("defaultBrowserLanguage");
+    let menulist = document.getElementById("primaryBrowserLocale");
     let menupopup = menulist.querySelector("menupopup");
     menupopup.textContent = "";
     menupopup.appendChild(fragment);
@@ -1114,7 +1114,7 @@ var gMainPane = {
     }
 
     messageBar.hidden = false;
-    gMainPane.selectedLocales = locales;
+    gMainPane.selectedLocalesForRestart = locales;
   },
 
   hideConfirmLanguageChangeMessageBar() {
@@ -1156,11 +1156,11 @@ var gMainPane = {
   },
 
   /* Show or hide the confirm change message bar based on the new locale. */
-  onBrowserLanguageChange(event) {
+  onPrimaryBrowserLanguageMenuChange(event) {
     let locale = event.target.value;
 
     if (locale == "search") {
-      gMainPane.showBrowserLanguages({ search: true });
+      gMainPane.showBrowserLanguagesSubDialog({ search: true });
       return;
     } else if (locale == Services.locale.appLocaleAsBCP47) {
       this.hideConfirmLanguageChangeMessageBar();
@@ -1341,7 +1341,7 @@ var gMainPane = {
     );
   },
 
-  showBrowserLanguages({ search }) {
+  showBrowserLanguagesSubDialog({ search }) {
     // Record the telemetry event with an id to associate related actions.
     let telemetryId = parseInt(
       Services.telemetry.msSinceProcessStart(),
@@ -1350,7 +1350,11 @@ var gMainPane = {
     let method = search ? "search" : "manage";
     gMainPane.recordBrowserLanguagesTelemetry(method, telemetryId);
 
-    let opts = { selected: gMainPane.selectedLocales, search, telemetryId };
+    let opts = {
+      selectedLocalesForRestart: gMainPane.selectedLocalesForRestart,
+      search,
+      telemetryId,
+    };
     gSubDialog.open(
       "chrome://browser/content/preferences/dialogs/browserLanguages.xhtml",
       { closingCallback: this.browserLanguagesClosed },
@@ -1370,12 +1374,12 @@ var gMainPane = {
     // Prepare for changing the locales if they are different than the current locales.
     if (selected && selected.join(",") != active.join(",")) {
       gMainPane.showConfirmLanguageChangeMessageBar(selected);
-      gMainPane.setBrowserLocales(selected[0]);
+      gMainPane.updatePrimaryBrowserLanguageUI(selected[0]);
       return;
     }
 
     // They matched, so we can reset the UI.
-    gMainPane.setBrowserLocales(Services.locale.appLocaleAsBCP47);
+    gMainPane.updatePrimaryBrowserLanguageUI(Services.locale.appLocaleAsBCP47);
     gMainPane.hideConfirmLanguageChangeMessageBar();
   },
 
diff --git a/browser/components/preferences/tests/browser_browser_languages_subdialog.js b/browser/components/preferences/tests/browser_browser_languages_subdialog.js
index a613622e7cb5c..6e1f9a08c0776 100644
--- a/browser/components/preferences/tests/browser_browser_languages_subdialog.js
+++ b/browser/components/preferences/tests/browser_browser_languages_subdialog.js
@@ -223,8 +223,8 @@ async function selectLocale(localeCode, available, selected, dialogDoc) {
 async function openDialog(doc, search = false) {
   let dialogLoaded = promiseLoadSubDialog(BROWSER_LANGUAGES_URL);
   if (search) {
-    doc.getElementById("defaultBrowserLanguageSearch").doCommand();
-    doc.getElementById("defaultBrowserLanguage").menupopup.hidePopup();
+    doc.getElementById("primaryBrowserLocaleSearch").doCommand();
+    doc.getElementById("primaryBrowserLocale").menupopup.hidePopup();
   } else {
     doc.getElementById("manageBrowserLanguagesButton").doCommand();
   }
@@ -703,7 +703,7 @@ add_task(async function testDownloadEnabled() {
   });
   let doc = gBrowser.contentDocument;
 
-  let defaultMenulist = doc.getElementById("defaultBrowserLanguage");
+  let defaultMenulist = doc.getElementById("primaryBrowserLocale");
   ok(
     hasSearchOption(defaultMenulist.menupopup),
     "There's a search option in the General pane"
@@ -731,7 +731,7 @@ add_task(async function testDownloadDisabled() {
   });
   let doc = gBrowser.contentDocument;
 
-  let defaultMenulist = doc.getElementById("defaultBrowserLanguage");
+  let defaultMenulist = doc.getElementById("primaryBrowserLocale");
   ok(
     !hasSearchOption(defaultMenulist.menupopup),
     "There's no search option in the General pane"
@@ -775,7 +775,7 @@ add_task(async function testReorderMainPane() {
   let messageBar = doc.getElementById("confirmBrowserLanguage");
   is(messageBar.hidden, true, "The message bar is hidden at first");
 
-  let available = doc.getElementById("defaultBrowserLanguage");
+  let available = doc.getElementById("primaryBrowserLocale");
   let availableLocales = Array.from(available.menupopup.children);
   let availableCodes = availableLocales
     .map(item => item.value)
diff --git a/browser/themes/shared/preferences/preferences.inc.css b/browser/themes/shared/preferences/preferences.inc.css
index 5397dc67a3c38..26736c5287e5c 100644
--- a/browser/themes/shared/preferences/preferences.inc.css
+++ b/browser/themes/shared/preferences/preferences.inc.css
@@ -1072,7 +1072,7 @@ menulist[indicator=true] > menupopup menuitem[indicator=true]:not([image]) > .me
   margin-inline-start: 4px;
 }
 
-#defaultBrowserLanguage {
+#primaryBrowserLocale {
   margin-inline-start: 0;
   min-width: 20em;
 }