It's place of origin has not yet been recorded.
Meaning cunt or pussy, it is typically considered a foul word as it is often used to refer to or describe something with great disgust.
It can be used as to refer to something or someone in an impolite manner.
It's most common usage is in reference to someone else's mother.
Jou ma se poes (literally- your mother's cunt)
In reference to someone distastefully:
Joe: Tony, you watch Dr. Phil last night?
Tony: That poes never knows what he's talking about.
In reference to an inanimate object with distaste:
Joe: Get out and push, Tony.
Tony: This car's poes, man.
P.O.S can stand for many things, such as Piece of Shit, Product of Society, Pissed off Stef, Promise of Skill, and Promise of Stress. He says it stands for whatever fits the song.
As of June 2010, he has three albums: Ipecac Neat, Audition, and Never Better
Jack: "That's P.O.S."
Mercedes: "Who's P.O.S?"
Jack: "A rapper coming from of the Great State of Minnesota."