The term is derived from the fact that partakers in such tomfoolery are usually trying to compensate for the fact that they have very small peni.
Louis: Right, I'm going to set my alarm for ten past eight. What time are you getting up, Tim?
Tim: Hmm, I think I'll set my alarm for, let's see, 8:09.
Ian: Oh, what lovely mashed potatoes! And just the right amount, too! Louis, are you not going to finish yours? Can't you manage them?
*Louis is stuffed and looks sick*
Ian: Well, I think I've just got room for some fruit! I'll have a satsuma.
Louis: Well in that case, I'll have a bag of satsumas.
*Louis proceeds to "down" a good ten satsumas*