ISO 639-3

The ISO 639-3 is the third version of a set of international standards that lists short codes for language names. Such codes are also known as language codes. Before this version was out, there was already ISO 639-1 and ISO 639-2, but due to the increase in languages being added to the database, ISO639-3 was therefore released, and all language codes have three letters, unlike the previous two, which allowed two letters in the code.
Each known language has a 3 letter code, and requests to add additional languages into the database can be made at the SIL International website. The standard was published by ISO on 2007-02-05.