From where is taken Alpha 3 language extension in windows/delphi?

Question

Under delphi, when I click Project > Language > add I can see a list of language with an alpha 3 extension code (example: afk for Afrikaans, aze for Azeri, fra for french, etc.) Those alpha 3 code are not ISO 639-3 alpha 3 code! so where are those alpha 3 code are coming from? those code seam to be related to windows and not to Delphi, but I can find from where exactly.

Note: under Windows 10, the Project > Language > add show many languages with ZZZ as extension, like ZZZ for Dzongkha, what it's mean?

Answer 1

AFAIK, that string is taken from a call to GetLocaleInfo with LCType set to LOCALE_SABBREVLANGNAME.

See: LOCALE_SABBREV* Constants