Grounder language often sounds like American English and slang just developed further over the years. Ex: "Your fight is over" sounds a bit like it came from "Your gunplay is all done" and "again" sounds like "another time"
This is my favorite thing for Octavia ever. She goes through so much developement and doesn't really fit anywhere. Not a Grounder. Not a Sky person. She is something her and her brother created all on their own. My fav character.