"Brain" as Slang for "Oral Sex": fun with metonymy

[Mullins, Bill]

>what's the motivation for "brains" 'scrotum'?  is it based on the
>expression "have balls for brains" '[of a man] think with one's
>genitals'?  or on a perceived physical similarity between a testicle
>and a brain?  or what?

Does this mean that the left testicle is the artistic one, and the right
testicle is the logical one?  <G>

>one of the categories i call "peekaboo"; this is where a guy's
>equipment sort of spills out of his confining clothing.  there are many
>subtypes of the peekaboo display, among them the through-the-fly
>escapee (which tends to look really silly, probably because it's the
>classic flasher pose).

I recently saw a frame grab from an episode of "Three's Company" in which
you could definitely see some of John Ritter's equipment, peeking out of a
pair of athletic shorts he was wearing.