From Where Do Alien Languages Like Na’vi Come From?:
Commissioning an entirely new language, which felt special for the first Avatar, is becoming a staple for immersive science-fiction and fantasy worlds. We’ve seen the invention of Dothraki and High Valyrian for HBO’s Game of Thrones, spoken and sign languages for the recent Dune remake, and bloodsucker-speak for Vampire Academy, to name only a handful. These languages are as functional as English, with internally consistent rules. In turn, neuroscientists have been able to harness them to better understand how the human brain processes constructed and natural languages, giving us new clues into what, exactly, constitutes a language to begin with.