The provenance of the data in this table is unknown. Possibly some of it comes from an earlier version of this CLDR file: https://phabricator.wikimedia.org/diffusion/ECLD/browse/master/LocalNames/LocalNamesEn.php

For Wikipedia / MediaWiki language code-to-name needs (because MediaWiki codes / names sometimes differ from ISO 639 / IANA standards) consider using this:

local wiki_lang_names_table = mw.language.fetchLanguageNames(mw.getContentLanguage():getCode(), 'all')	-- table of language codes and names (indexed by code) known to MediaWiki

The above will always be current with MediaWiki whereas this module is not. documentation