fuck (v.)
"to have sexual intercourse with" (transitive), until recently a difficult word to trace in usage, in part because it was omitted as taboo by the editors of the original OED when the "F" entries were compiled (1893-97). Johnson also had excluded the word, and fuck wasn't in a single English language dictionary from 1795 to 1965. "The Penguin Dictionary" broke the taboo in the latter year. Houghton Mifflin followed, in 1969, with "The American Heritage Dictionary," but it also published a "Clean Green" edition without the word, to assure itself access to the public high school market.
Written form attested from at least early 16c.; OED 2nd edition cites 1503, in the form fukkit, and the earliest attested appearance of current spelling is 1535 ("Bischops ... may fuck thair fill and be vnmaryit" [Sir David Lyndesay, "Ane Satyre of the Thrie Estaits"]). Presumably it is a more ancient word, but one not written in the kind of texts that have survived from Old English and Middle English [September 2015: the verb appears to have been found recently in an English court manuscript from 1310]. Buck cites proper name John le Fucker from 1278, but that surname could have other explanations. The word apparently is hinted at in a scurrilous 15c. poem, titled "Flen flyys" ["Fleas, Flies (and Friars)"], written in bastard Latin and Middle English. The relevant line reads:
Non sunt in celi
quia fuccant uuiuys of heli
"They [the monks] are not in heaven because they fuck the wives of [the town of] Ely." Fuccant is pseudo-Latin, and in the original it is written in cipher. The earliest examples of the word otherwise are from Scottish, which suggests a Scandinavian origin, perhaps from a word akin to Norwegian dialectal fukka "copulate," or Swedish dialectal focka "copulate, strike, push," and fock "penis."
https://www.etymonline.com/word/fuck