as for the op: what the hell did you think a thrasher was?
Well I originally thought the logo was a hurricane (it really does look like it without looking at it in a big picture), so I thought "thrasher" was just a way to describe the hurricane because it thrashes everything in its way.
Since this is now a thread for embarrassing NHL related confessions, I reveal that I noticed the first h in Thrashers only a couple of weeks ago. Wasn't exactly sure what "trashers" supposedly were, I guess some kind of destroyers putting their opponents in the trash. Well turns out they mean more or less the same (apart from a thrasher also being a bird). Booo such a lame anticlimax!!