On Wed, 14 Jul 2004 12:38:56 -0400, Jeff Wisnia
vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email
And also
http://www.askoxford.com/asktheexper...s/brassmonkeys
which bears you out.

I would say that the original was indeed ribald, but the second
explanation was thought up to appease (or humour) "polite company"
http://www.snopes.com/language/stories/brass.htm