Fuck, cunt, cock, shit, ass, most of those vulgar words, are the old english/anglo saxon equivalents of Latin words that aren't considered vulgar now, like vagina, defecate/feces, whatever. They weren't vulgar at all to regular old english speakers
The words were considered low by the nobles, the clergy, who preferred French or Latin, to English, and that, mixed with the functions they represented, made those words vulgar.
Linguistics GO!
Stone