who makes up the crazy fake languages in movies? lol at that job title!
 

Blaha blaga jag jaga git jigggy jiggy wit it

ok now stop to make fun with people from burundi. Don't be a racist

Some movie directors have hired linguists to come up with fake languages, sometimes with consistent grammatical structures and more. For example, Klingon in Star Trek. Tolkien's books were originally written as vehicles for him to show off his fully developed "conlangs" (constructed languages).

Linguists. Thats the logical assumption....

Or to phrase another way... some guys get paid to make up jibberish