fuckfuck

The story

Possibly attested in a 772 CE charter that mentions a place called Fuccerham, which may mean "hām (‘home’) of the fucker" or "hamm (‘pasture’) of the fucker"; a John le Fucker in a record from 1278 may just be a variant of Fulcher; compare Fucher, Foker, etc. The earliest unambiguous use of the word in a clearly sexual context, in any stage of English, appears to be in court documents from Cheshire, England, which mention a man called Roger Fuckebythenavele (possibly tongue-in-cheek or directly suggestive of a depraved sexual act) on 8 December 1310. It was first listed in a dictionary in 1598. Scots fuk or fuck is attested slightly earlier, probably reinforcing the Northern Germanic/Scandinavian origin theory.1disputed Scholars disagree here; the competing view is quoted as the source gives it. A range of folk-etymological backronyms, such as fornication under consent of the king and for unlawful carnal knowledge, are all demonstrably false.2folk etymology The source marks this as unproven or a folk etymology. Quoted, not asserted.

Full etymology on Wiktionary