Thread:User talk:WaitingforGodot/I like you, Godot, but I'm going to have to call bullshit on that/reply (24)

"cis" means same side, "trans" means opposite side. Which makes some degree of sense with cis-gender and trans-gender. Though I'm not sure if that's the actual etymology, for instance until I heard people actually use the term "cis", I assumed "trans" was some shortening of "transferring" or "transitioning" or something like that.