From hose (“to siphon gasoline from automobile gas tanks”).
hoser (plural hosers)
- (Canada, slang) Back when Hockey was played on frozen ponds and lakes the losers of the hockey game would have to hose the lakes to become clean, smooth ice. They were tagged "Hosers".
- (Canada, slang) A clumsy, boorish person, especially an uncouth, beer-drinking man.
- (Canada, slang) A person whose self interest often outweighs any ethical considerations.
- (Canada, slang) Not an overtly criminal individual, but one known to participate in petty infractions and rule bending. Example: A hoser would consume food or alcoholic beverages, typically pizza and beer, with complete disregard to ownership or sharing.
Usage notes 
The phrase was made popular by a sketch on the television show SCTV, by Bob and Doug McKenzie (Rick Moranis and Dave Thomas.) It often follows "take off", as in to go away, or stop being a hoser.
During the Great Depression of the 1930s, it was a term used to describe Canadian farmers who would siphon gas from farming vehicles. This Canadian expression has also been used to describe the players on the losing side of a game of shinny. In the old days, such losers would have to hose down the rink after the game.
In the early ‘80s, “hoser” gained cult status after being bandied about and branded by the SCTV characters Bob & Doug McKenzie, whose iconic Canadian status boomed with the movie Strange Brew and a hilarious Christmas album. Bob and Doug are prototypical hosers; they are absentminded fools from the Canadian suburbs who drink beer, watch hockey, wear toques, smoke cigarettes, and say things like, “No way. Take off, you hoser.” Today, anyone who still wears a flannel lumberjack jacket, eats too many doughnuts and collects welfare cheques risks being labeled a hoser.