diff --git a/widget/cocoa/nsMenuItemX.h b/widget/cocoa/nsMenuItemX.h
index 26f1170bcc69..8576cf56f37a 100644
--- a/widget/cocoa/nsMenuItemX.h
+++ b/widget/cocoa/nsMenuItemX.h
@@ -62,7 +62,7 @@ class nsMenuItemX final : public nsMenuObjectX, public nsChangeObserver {
   void SetupIcon();
 
  protected:
-  void UncheckRadioSiblings(nsIContent* inCheckedElement);
+  void UncheckRadioSiblings(nsIContent* aCheckedElement);
   void SetKeyEquiv();
 
   EMenuItemType mType;
diff --git a/widget/cocoa/nsMenuItemX.mm b/widget/cocoa/nsMenuItemX.mm
index d8c9762f830c..0d1759e31e5d 100644
--- a/widget/cocoa/nsMenuItemX.mm
+++ b/widget/cocoa/nsMenuItemX.mm
@@ -180,16 +180,16 @@ nsresult nsMenuItemX::DispatchDOMEvent(const nsString& eventName, bool* preventD
 
 // Walk the sibling list looking for nodes with the same name and
 // uncheck them all.
-void nsMenuItemX::UncheckRadioSiblings(nsIContent* inCheckedContent) {
+void nsMenuItemX::UncheckRadioSiblings(nsIContent* aCheckedContent) {
   nsAutoString myGroupName;
-  if (inCheckedContent->IsElement()) {
-    inCheckedContent->AsElement()->GetAttr(kNameSpaceID_None, nsGkAtoms::name, myGroupName);
+  if (aCheckedContent->IsElement()) {
+    aCheckedContent->AsElement()->GetAttr(kNameSpaceID_None, nsGkAtoms::name, myGroupName);
   }
   if (!myGroupName.Length()) {  // no groupname, nothing to do
     return;
   }
 
-  nsCOMPtr<nsIContent> parent = inCheckedContent->GetParent();
+  nsCOMPtr<nsIContent> parent = aCheckedContent->GetParent();
   if (!parent) {
     return;
   }
@@ -197,7 +197,7 @@ void nsMenuItemX::UncheckRadioSiblings(nsIContent* inCheckedContent) {
   // loop over siblings
   for (nsIContent* sibling = parent->GetFirstChild(); sibling;
        sibling = sibling->GetNextSibling()) {
-    if (sibling != inCheckedContent && sibling->IsElement()) {  // skip this node
+    if (sibling != aCheckedContent && sibling->IsElement()) {  // skip this node
       // if the current sibling is in the same group, clear it
       if (sibling->AsElement()->AttrValueIs(kNameSpaceID_None, nsGkAtoms::name, myGroupName,
                                             eCaseMatters)) {
diff --git a/widget/cocoa/nsMenuUtilsX.h b/widget/cocoa/nsMenuUtilsX.h
index deee16718260..c4f8fc480297 100644
--- a/widget/cocoa/nsMenuUtilsX.h
+++ b/widget/cocoa/nsMenuUtilsX.h
@@ -23,7 +23,7 @@ uint8_t GeckoModifiersForNodeAttribute(const nsString& modifiersAttribute);
 unsigned int MacModifiersForGeckoModifiers(uint8_t geckoModifiers);
 nsMenuBarX* GetHiddenWindowMenuBar();   // returned object is not retained
 NSMenuItem* GetStandardEditMenuItem();  // returned object is not retained
-bool NodeIsHiddenOrCollapsed(nsIContent* inContent);
+bool NodeIsHiddenOrCollapsed(nsIContent* aContent);
 int CalculateNativeInsertionPoint(nsMenuObjectX* aParent, nsMenuObjectX* aChild);
 
 // Find the menu item by following the path aLocationString from aRootMenu.
diff --git a/widget/cocoa/nsMenuUtilsX.mm b/widget/cocoa/nsMenuUtilsX.mm
index f12e88ed1d11..c59c808c9b60 100644
--- a/widget/cocoa/nsMenuUtilsX.mm
+++ b/widget/cocoa/nsMenuUtilsX.mm
@@ -179,12 +179,12 @@ NSMenuItem* nsMenuUtilsX::GetStandardEditMenuItem() {
   NS_OBJC_END_TRY_ABORT_BLOCK;
 }
 
-bool nsMenuUtilsX::NodeIsHiddenOrCollapsed(nsIContent* inContent) {
-  return inContent->IsElement() &&
-         (inContent->AsElement()->AttrValueIs(kNameSpaceID_None, nsGkAtoms::hidden,
-                                              nsGkAtoms::_true, eCaseMatters) ||
-          inContent->AsElement()->AttrValueIs(kNameSpaceID_None, nsGkAtoms::collapsed,
-                                              nsGkAtoms::_true, eCaseMatters));
+bool nsMenuUtilsX::NodeIsHiddenOrCollapsed(nsIContent* aContent) {
+  return aContent->IsElement() &&
+         (aContent->AsElement()->AttrValueIs(kNameSpaceID_None, nsGkAtoms::hidden, nsGkAtoms::_true,
+                                             eCaseMatters) ||
+          aContent->AsElement()->AttrValueIs(kNameSpaceID_None, nsGkAtoms::collapsed,
+                                             nsGkAtoms::_true, eCaseMatters));
 }
 
 // Determines how many items are visible among the siblings in a menu that are
diff --git a/widget/cocoa/nsMenuX.h b/widget/cocoa/nsMenuX.h
index ce68ac33df84..384d19efe070 100644
--- a/widget/cocoa/nsMenuX.h
+++ b/widget/cocoa/nsMenuX.h
@@ -73,9 +73,9 @@ class nsMenuX final : public nsMenuObjectX, public nsChangeObserver {
   bool OnClose();
   void AddMenuItem(mozilla::UniquePtr<nsMenuItemX>&& aMenuItem);
   void AddMenu(mozilla::UniquePtr<nsMenuX>&& aMenu);
-  void LoadMenuItem(nsIContent* inMenuItemContent);
-  void LoadSubMenu(nsIContent* inMenuContent);
-  GeckoNSMenu* CreateMenuWithGeckoString(nsString& menuTitle);
+  void LoadMenuItem(nsIContent* aMenuItemContent);
+  void LoadSubMenu(nsIContent* aMenuContent);
+  GeckoNSMenu* CreateMenuWithGeckoString(nsString& aMenuTitle);
 
   nsTArray<mozilla::UniquePtr<nsMenuObjectX>> mMenuObjectsArray;
   nsString mLabel;
diff --git a/widget/cocoa/nsMenuX.mm b/widget/cocoa/nsMenuX.mm
index c506108ebc4e..602143a9681a 100644
--- a/widget/cocoa/nsMenuX.mm
+++ b/widget/cocoa/nsMenuX.mm
@@ -435,11 +435,11 @@ nsresult nsMenuX::GetEnabled(bool* aIsEnabled) {
   return NS_OK;
 }
 
-GeckoNSMenu* nsMenuX::CreateMenuWithGeckoString(nsString& menuTitle) {
+GeckoNSMenu* nsMenuX::CreateMenuWithGeckoString(nsString& aMenuTitle) {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
-  NSString* title = [NSString stringWithCharacters:(UniChar*)menuTitle.get()
-                                            length:menuTitle.Length()];
+  NSString* title = [NSString stringWithCharacters:(UniChar*)aMenuTitle.get()
+                                            length:aMenuTitle.Length()];
   GeckoNSMenu* myMenu = [[GeckoNSMenu alloc] initWithTitle:title];
   myMenu.delegate = mMenuDelegate;
 
@@ -457,25 +457,25 @@ GeckoNSMenu* nsMenuX::CreateMenuWithGeckoString(nsString& menuTitle) {
   NS_OBJC_END_TRY_ABORT_BLOCK;
 }
 
-void nsMenuX::LoadMenuItem(nsIContent* inMenuItemContent) {
-  if (!inMenuItemContent) {
+void nsMenuX::LoadMenuItem(nsIContent* aMenuItemContent) {
+  if (!aMenuItemContent) {
     return;
   }
 
   nsAutoString menuitemName;
-  if (inMenuItemContent->IsElement()) {
-    inMenuItemContent->AsElement()->GetAttr(kNameSpaceID_None, nsGkAtoms::label, menuitemName);
+  if (aMenuItemContent->IsElement()) {
+    aMenuItemContent->AsElement()->GetAttr(kNameSpaceID_None, nsGkAtoms::label, menuitemName);
   }
 
   // printf("menuitem %s \n", NS_LossyConvertUTF16toASCII(menuitemName).get());
 
   EMenuItemType itemType = eRegularMenuItemType;
-  if (inMenuItemContent->IsXULElement(nsGkAtoms::menuseparator)) {
+  if (aMenuItemContent->IsXULElement(nsGkAtoms::menuseparator)) {
     itemType = eSeparatorMenuItemType;
-  } else if (inMenuItemContent->IsElement()) {
+  } else if (aMenuItemContent->IsElement()) {
     static Element::AttrValuesArray strings[] = {nsGkAtoms::checkbox, nsGkAtoms::radio, nullptr};
-    switch (inMenuItemContent->AsElement()->FindAttrValueIn(kNameSpaceID_None, nsGkAtoms::type,
-                                                            strings, eCaseMatters)) {
+    switch (aMenuItemContent->AsElement()->FindAttrValueIn(kNameSpaceID_None, nsGkAtoms::type,
+                                                           strings, eCaseMatters)) {
       case 0:
         itemType = eCheckboxMenuItemType;
         break;
@@ -486,11 +486,11 @@ void nsMenuX::LoadMenuItem(nsIContent* inMenuItemContent) {
   }
 
   AddMenuItem(
-      MakeUnique<nsMenuItemX>(this, menuitemName, itemType, mMenuGroupOwner, inMenuItemContent));
+      MakeUnique<nsMenuItemX>(this, menuitemName, itemType, mMenuGroupOwner, aMenuItemContent));
 }
 
-void nsMenuX::LoadSubMenu(nsIContent* inMenuContent) {
-  AddMenu(MakeUnique<nsMenuX>(this, mMenuGroupOwner, inMenuContent));
+void nsMenuX::LoadSubMenu(nsIContent* aMenuContent) {
+  AddMenu(MakeUnique<nsMenuX>(this, mMenuGroupOwner, aMenuContent));
 }
 
 // This menu is about to open. Returns TRUE if we should keep processing the event,