Well, the actual keyword is retum. It turns out that most humans can't tell the difference between an r and an n next to each other, or the letter m, so they just decided to go with the quicker to type 'm' instead or 'rn' You've just been reading it wrong.

:D Honestly, I think either ret or return is fine, but I'd match other keywords. So if you're using pub and priv instead of public and private, I'd use ret instead of return as well.