There is a BBC list of the ten worst words to use, and as a former employee of theirs, I can confirm the "c" word tops it. Misspelt by current standards, it occurs more than once in Chaucer's Canterbury Tales. Both London and Oxford had "Grope c word" lanes and yes they were where prostitutes plied their trade.
Really though, the Victorians created the modern definition of a rude word. At that time, the word was more applied to the rustic or rural meaning and as such, nice descriptive Anglo-Saxon words were in common usage by, for want of a better term, the less educated. So the words became rude ones. Then of course some animal names needed changing as part of them was a rude word, 'Whitearse' being what we now call the "Wheat ear". Said bird has nothing to do with wheat, no more observable ears than any other bird, but does have a white bottom.