An almost sarcastic response to something so seemingly simple you shouldn't have to ask the question to begin with. Could also be an affectionate term meaning again that the answer should be obvious but you just missed it. It is said so quickly, it almost sounds like one long word.
"He's owes me money that's why you haven't seen him. You don't know? He better not come around here".
Guy to his girl "I love you shorty, you don't know?"