In French they often use the word "autochthone" as an equivalent for "indigenous". Its opposite is "allochthone".
I learned this from some comrades a few years ago, it came up in either a presentation or a zine.
You see this one a lot in a certain sort of nerd content, ttrpgs, some fantasy novels.
Is that where the name of the Warhammer 40k planet Cthonia comes from? If so, that's kind of clever word play, as it literally just means "Earth", and also the allusion to Cthulhu might be meant to evoke the sinister nature of Horus.
Alongside the 40k planet "Birmingham", which is very dark and nobody goes there.
Wtf I learned this word like a week ago and now it's truly everywhere. I don't just mean that phenomenon where you notice new words more after learning their definition, I have never seen this cluster of syllables in my life until all of a sudden I can't escape