Monger n.
From the root term Cock Monger. The name came about with the need for derogatory nicknames. The name Cock Monger was originally meant for a specific member of a group. The name caught on so well that soon it became a generic nickname, later shortened to just monger, mainly because we're lazy bastards and cock monger takes up too many syllables.
Synonyms: Dickhead, asshole, asswipe, shit head, nut, sack, dumbass, etc.