It comes from the meaning of the words "me", "you", "he/she". These are first person singular, second person singular and third person singular.
So when you play a "first person shooter" you are seeing things from what are supposed to be your in-game eyes. In a third person shooter, you're seeing from another perspective, usually one following behind the character.
I'm not sure what could be described as a "second person" viewpoint. I suppose if they showed the game from the perspective of a relevant party who you are not in control of, it could be considered "second person". If you can imagine playing half-life, and controlling Gordon Freeman, but your screen only shows the viewpoint of one of the soldiers/aliens. Obviously, that is not practical for a game.
A game I'm developing with some friends:
www.xnagg.com/zombieasteroids/publish.htm
It is largely a technical exercise but feedback is appreciated.
