Public Service Announcement: If you ever need to add a very obscure #language to a piece of software and you can't find an #ISO 639 code for it, remember that ISO 639-2 defines a special range for that.
All codes between "qaa" and "qtz" (inclusive) are free to be used for anything.
So just use one of those instead of hacking some ugly special case in your #software or adding some non-standard code.