Well, I think its more of an American term, but when someone says Johnson, do you think "wang"?
Sad truth of today is that if you're called Richard, or know a Richard, or see Richard, people say "we should say Dick, lolololol". I mean if Friends can go like 10 years without the joke, and even over 3 Austin Powers movies its not mentioned, how is it possible people find it funny? Its weird.