I like that there isn't a clan doc for the rinth, for two reasons. First, the rinth (in my mind at least) is huge, much bigger than a given tribe, so there'd be a lot of differences, not just east and west side, but smaller cultures within, and below. Second, it allows players to fill in this space. The rinth has always (for better or worse) been a wild wild west in terms of play, with minimal cultural documentation, where you can have all sorts of strange monsters and monstrosities.
That said, one spot to pick up on 'jargon' is the rumor boards. When I first started playing, I learned terms like 'pitchcloak' (a soldier in the Arm) and 'southsider' from the rumor boards in the rinth.