Even his default first name, Peter, is a word variation for a dick. Naming him Richard would continue the double entendre theme.
The
official nicknames for Richard includes Dick, so that would have been obvious and would not "continue the double entendre" as much as you think. The usual struggle would be to
NOT call a richard you just met dick.
(Consider this an RL tip, superiors at work often are quite ... allergic to that nickname)
Both the mummy roommate and the succubus secretary would have called him that immediately, though. One does not care and the other wants his dick from the beginning.
The name itself is derived from germanic and translates basically to "strong in rule" though.
The thought process for naming a protagonist usually is a lot more intricate and thorough than many people think.