Its douche bag spelled backwards. But its a way to one up someone if you get into a childish 3rd grade style war of words. Often leaving your opponent confused and weary of what lies next for him.
Note: The "e" is silent, so don't pronounce it, or you'll look like the gab choud
Wesley - You are a weiner.
Vladmir - Yeah, well your a Gab Echoud.
Wesley - What did you call me? I'm so confused. I suck at life.