You asked for it, Michael.
It’s been called many things. The F word. The Big F---. Personally, I prefer f*ck. I remember being little and how feared and yet revered the word was, like just saying it would conjure up a storm that would obliterate everything you loved. Or at least bring the wrath of every adult within a mile radius. I’m not the only one who treats it so. Go look at the Online Etymology Dictionary’s entry on it. It’s an entire freaking page.
It can be traced all the way back to 1503 as fukkit (does that need an asterisk?) It’s hard to trace it further because as a “bad” word it wasn’t used in most of the literature that survived in that era, most of which was probably written by monks, who I’m guessing didn’t use it much. It wasn’t until last century that the word was even allowed in print.
There is no proof, but it might relate to fukka, a word for sex in Norwegian dialect, or focka in Swedish, which has a similar meaning. Another theory is that it came from the Middle English fyke/fike, which can mean flirt or restlessly fidget. Again, no proof, but it is true that the f word only appears in Germanic languages, so obviously it first showed up in some Proto-German dialect.
One thing that is for certain is that those stories about it being an acronym for Fornication Under Consent of King or For Unlawful Carnal Knowledge are hogwash, proving once again that on the internet, anyone will believe anything.
The Online Etymology Dictionary, of course.
And that site that's so old that it only exists now as an archived text file.