The language buttons in the preferences have their localized names in their hint tooltips

For example, if you hover over the "English" button while the language is Greek, the hint tooltip will be "Αγγλικά", which is the Greek word for English.

Scripts/Dialogs/PreferencesDialog.gd

@@ -20,6 +20,7 @@ func _ready() -> void:
 	for child in languages.get_children():
 		if child is Button:
 			child.connect("pressed", self, "_on_Language_pressed", [child])
+			child.hint_tooltip = child.name
 
 	for child in themes.get_children():
 		if child is Button: