Kartographer uses the content language of the wiki as the default for label language. This can be changed with this setting for just this map.
Use local instead of a language name to show all labels in the language local to that location. For example, city names in Mexico would be displayed in Spanish, while city names in Japan would be displayed in Japanese.
When labels are not available in the language chosen, Kartographer follows a fallback process. For more information on how this works see the Kartographer help page.