mine came from way back in the day (1999) when i lived in van nuys, ca. when i first moved from idaho to los angeles and didn't know shit about anything, i became really good friends with this couple called Sid and Barbie. We got along really well, and i got an apartment and let them move in, with the promise they would get jobs and help me out. anyways, after 3 months and many many ridiculous parties, they still hadn't gotten jobs and i finally lost it and kicked them out. they came back a week later and broke into my apartment and stole everything i had, including my checkbook! they ended up writing a bunch of bad checks and i couldn't pay rent, so i got evicted.
i left los angeles for a few months after that, feeling really angry about life, and the ideals of "punk rock" and (what my conception of which was at the time) anarchy. so like i said i was really angry a lot of the time about how no one really cared about their ideals and they were all just a bunch of fashion punks. and i drank a LOT. so my name came mostly from being angry and being drunk (the UK english slang for drunk = pist).
it's kinda ironic nowadays, as im an extremely nice/laid back guy, and you REALLY have to push my buttons to piss me off. it's generally pretty hard to make me mad. also, im not nearly as bad of a drunk as i used to be. i would like to have a new name honestly, but at this point everyone knows me by it, so it's kinda hard to escape