despite the word sounding and literally basically being the beginning of 'penis', this word has nothing to do with your obscene love sword! Unless you wish to use it in modern day times, in which case it is indeed short for the word 'penis' and can be used as a fairly rude insult.
In reality, the word peen means the back of a
hammer. You know, that one part of the hammer that's round and at the back? Yes, that part. It's not a penis.
stop calling it that.
It's also called a ball-peen. It's still not a penis. Never
will be. Unless your.... That
guy.
Person: nice ball-peen, phil!
Phil : Yeah my dicks real nice ain't it?
Person: I was
talking about your
hammer.
Phil: That's stupid you're stupid
stop saying thAT