origin: at the site of a "sour" person, you make a "sour" face, as such when you suck a lemon.
Oh snap. DW's lookin pretty sour as usual.
2. When you use it to describe another person's actions. Oh no she didn't!
Chase: "That is oh so sour."
ex2. Derek: "You're a dirty whore."
Lauren: "Oh no you sick and souuur!"