Someone who picks cigarette end up off the pavement/ashtray or where ever else they might be and smokes them, or maybe keeps them in a collection. Usually used as an insult by chavs
guy: Hey look, i found a half-smoked cigarette!
chav: fuckin docker picker! (punches him with a hand covered in cheap gold rings from argos)
Made popular by the comedian Donnie Baker on the Bob and Tom radio show. Docker Diver is a homosexual who enjoys giving oral sex to another homo wearing Dockers brand pants. On the Bob and Tom show Donnie uses this term to describe the radio personality Randy.
Who cares if you have a boat Randy cause everybody already knows your a docker diver. That ain't no secret. I swear to God its not.