I can't find it either now.
Mine comes from my surname (Campbell) and the popular (at the time I got it) kid's TV show Supergran. Supergran's "arch enemy" was The Scunner Campbell and my friends thought it such a wheeze to give me the name. My friends from that time still call me Scunner. If they call me Keith, I know something serious has happened or they want to borrow something
Usedbustickets will be interesting; personally I wonder about many user names on here, none more so than Slartibartfast