Spiffybeth ... to a foreigner to the English language, please: explain what it means (general meaning, other than "to use a water hose and spray water onto the lawn or flowers" or so). Please. For that is the only meaning of the expression I know, and - as you say - it does not apply. Nor does anything bawdy. So?
Hoser is both a slang term and a stereotype, originating from and used primarily in Canada. Like the very similar term hosehead, it originally referred to farmers of the Canadian prairies who would siphon gas from farming vehicles with a hose during the Great Depression of the 1930's. The expression has since been converted to the verb 'to hose' as in to trick, deceive, or steal - for example: "That card-shark sure hosed me." Hosed has an additional meaning of becoming drunk - for example: "Let's go out and get hosed."
The term "hoser" refers to an era in hockey before the ice resurfacing machine came into use. The losing team had to hose off the ice. The term "hoser" can then be construed to mean loser
(told ya a canadian could explain it, where's big mike when you need him? lol)