The Worrds "Shit" and "Fuck" - A Scholarly Treatise of their Uses and Etymoloty

[Homeless Nutter]

A Brief Etymology
Urban legend has it that the word “shit” was a nautical acronym. Back in the day when manure was shipped low in the belly of wooden ships, moisture would get in and the process of fermentation would release methane gas. This is a highly flammable gas. All it took was some fool to go down there with a lantern or cigarette and blow the whole thing to smithereens. So to keep the manure dry, they would stamp it with the acronym S.H.I.T. (Ship High In Transit).

Considering that the word "shit" has older forms, like "scite", or "scitte" the hypothesis, that it's an acronym is highly unlikely to be true.

Two urban legends claim to describe the etymology of the word “fuck.”
1. The word “fuck” owes its ontology to the Church. Then they used to hang people for engaging in sex outside of marriage, they would hang a sign over their bodies that read, “For Unlawful Carnal Knowledge.”
2. King Henry VIII engaged in royal pimpdom, would have the acronym F.U.C.K. tattooed on the necks of his girls. It stood for “Fornication Under Consent of the King.” When men saw that, they knew they had to pay the king.

Yeah, none of that is true either, I'm afraid. Which is usually the case with urban - or any other kind of - legends.
The actual etymology of "fuck" is not exactly clear, but as a general rule we can discount the idea, that acronyms had a major role in creating common words in the Middle Ages, or in fact as late as XIX century, because most people, who would use words like "shit" or "fuck" couldn't read.