In the summer of 823, Warlord Roytaa had claimed about a third of the Ease as his kingdom of decadence. He used nepotism and murder to replace most of the Bluecoats in the area with relatives, and he was creating quite a cesspit. He was into the occult, and conducted frequent rituals of protection and such, and a soothsayer once told him that he would be slain by Gapjaw, a crocolisk that drifted through the canals at the top of the food chain. So when this punk kid managed to surprise him in his quarters and knife him to death, Roytaa wanted to know how it was possible. The kid just grinned and said “I must be Gapjaw.” Sure, the kid was a smartass, but the more superstitious noted the crocolisk was never seen again. They wondered if this kid had somehow faced that monster in the darkness and taken its essence, just to kill the Warlord. Whether you believe the story or not, the name stuck.
From “Occult Vignettes of the Dusk,” by Sord Vortison