The Language of the Incan Empire

I think that if you're con-worlding, you could go either way. You could have invaders come in and promulgate a language not their own. For example, the language of the Incan Empire was Quechua. And various empires in the Tigris-Uphides area were happy to use Aramaic regardless of what they spoke. So any history you can imagine can be justified with actual real life human experience. It's simply a matter of how much time and brain power you have to determine how deep you want to go.