A person (usually male) who is pretentious and arrogant, but lacks any real skill or ability. Most often used by military pilots.
Around here, we got two kinds of pilots: the hotdogs who get all the hot planes, and then you got your pudknockers who dream of flying the hot planes. So, what are you two pudknockers gonna have?
The Latin word for "shame," some Victorian clown thought it would be a great euphemism for female genitalia, possibly because he felt shame for wanting to see some.