The water that collects in the spot under the "bridge" of your anus and groin, much like a troll that lives under a bridge.
Only good way to dry Troll Water is to do a Troll Sweep
Guy 1: Dude, this morning, i had Troll Water worse then ever before! And I forgot to Troll Sweep!
Guy 2: Oh, you must have really gotten your pants wet!
Guy 1: Yup.