So called, because the process is somewhat similar to the way in which one is forced to endure blue balls. While with blue balls, a girl won't finish you off sexually, in blue brains the victim has yet to have their curiosity "finished off." While blue balls is more painful, blue brains is often endured for longer periods of time and cannot be remidied on one's own.
Guy 1: Yo, you know what I heard about Lisa?
Guy 2: No, tell me.
Guy 1: Well, I really shouldn't say...
Guy 2: Come on you have to tell me!
Guy 1: I can't, I promised I wouldn't say anything.
Guy 2: Dude we've been talking about this for ages. Total blue brains.
Friend: Does it happen often?
Friend: He's probably suffering from Blue Brains.
Girl: But why? What would have caused it?
Friend: Most likely he's distracted by his Blue Balls.