A chickenass is
another word for cloaca, which I'm sure lots of
americans will say, but is actually another word for a really
stupid person (at a certain time)
It emphasises a person to being a chicken, but like if that's not enough, you just add ass because it has a ring to it.
Thus a guy named Pantoffelman from the town of Beglium started calling his friends chickenasses as of tomorrowland 2008.