There are several urban-legend false etymologies postulating an acronymic origin for the word. None of these acronyms was ever recorded before the 1960s, according to the authoritative lexicographical work The F-Word, and thus are backronyms.
I took my lumps in a previous post. Thank you for the supplementals.
EXACTLY. They were told as JOKES about the word back in the 60s! That revision of the origin also applies to the modern dictionaries so-called etymological history of the word. While it's definitely Germanic in origin (remember the Angles; Saxons, and Jutes?), it is unlikely that the word came from words meaning “to strike”, etc (it's more probable that those words evolved from the vulgar one!)
F-ck is one of several ancient words (many considered vulgar) that are echoic in origin, another such word is “piss.”