* Fin (as in a fish): This is a physical feature and not a language.
* Fin (as a shortened form of "final"): This is an English word meaning "ending" or "last."
* Fin (as an abbreviation): This could stand for a variety of things, but without further context, it's impossible to know what language it's associated with.
To understand what language "fin" might be referring to, you need to provide more context. For example, what is the sentence or phrase where you encountered this word?