It dates to the Norman Conquest back in 1066. All the Saxon words became bad because the Saxons lost and were enslaved. French words=good; Saxon words=bad. It's as simple as that. The Saxon terms became, quite literally, vulgar. (Latin: of the people, as opposed to the ruling class.) So, while I can easily write the words with French roots such as defecate, urinate, copulate, etc. without fear of reprisal, should I use the entirely synonymous Saxon equivalents, that would not be permitted and even would, by a fit of illiteracy on the part of the JREF moderators, be considered "obscene."
What bothers me is that, almost seven hundred years after the end of French feudalism and the establishment of English common law which led to the two longest-lived representative democracies on the planet, English-speakers still have enough of what amounts to a we're-not-French-enough inferiority complex to consider Saxon words bad.
It isn't even limited to so-called cuss words. "Pork," for some reason, is more acceptable than "swine flesh" or "pig flesh" and nobody even remembers "kine" for cattle, though "cow" survives. But, of course, the lower classes were the ones who tended the animals, so the old Saxon terms survived to described the animals, while their flesh (excuse me, meat) got the French terms when served up as haute cuisine.
Seriously. Four hundred years of slavery, and almost seven hundred years after it, Anglos still symbolically abase themselves in deference to their former masters. It must have been some pretty effective slavery. Even African-Americans do better than Anglos in this regard.