reduce-to-639-1
Quick and dirty tool to reduce language claims to two-letter iso-639-1 codes
iso-639-1-plus
Native language names for all ISO-639-1 codes plus some common IETF BCP 47 language tags
iso-locale-tools
All world countries and data points about them, as well as tools for interfacing with that data.
@olizilla/lol
A CLI tool to get a list of language names from a directory of locales