For no particular reason, the etymology of "fuck" came to mind... Germans say fuck freely, appropriation gone full circle.
The Oxford English Dictionary states that the ultimate etymology is uncertain, but that the word is "probably cognate" with a number of Germanic words with meanings involving striking, rubbing and having sex or is derivative of the Old French word that meant "to fuck."
The word has probable cognates in other Germanic languages, such as German ficken (to fuck); Dutch fokken (to breed, to beget); dialectal Norwegian fukka (to copulate), and dialectal Swedish focka (to strike, to copulate) and fock (penis). This points to a possible etymology where Common Germanic fuk- comes from an Indo-European root meaning "to strike", cognate with non-Germanic words such as Latin pugno "I fight" or pugnus "fist". By application of Grimm's law, this hypothetical root has the form *pug–. There is a theory that fuck is most likely derived from Flemish, German, or Dutch roots, and is probably not derived from an Old English root.
Latin and Greek cognates
There may be a kinship with the Latin futuere (futuo), a verb with almost exactly the same meaning as the English verb "to fuck". From fūtuere came French foutre, Catalan fotre, Italian fottere, Romanian futere, vulgar peninsular Spanish joder, Portuguese foder, and the obscure English equivalent to futter, coined by Richard Francis Burton. However, there is no clear past lineage or derivation for the Latin word. These roots, even if cognates, are not the original Indo-European word for to copulate, but Wayland Young argues that they derive from the Indo-European *bhu– or *bhug– ("be", "become"), or as causative "create" [see Young, 1964]. A possible intermediate might be a Latin 4th-declension verbal noun *fūtus, with possible meanings including "act of (pro)creating".
However, the connection to futuere has been disputed—Anatoly Liberman calls it a "coincidence" and writes that it is not likely to have been borrowed from the Low German precursors to fuck.
Greek phyō (φύω) has various meanings, including (of a man) "to beget", or (of a woman), "to give birth to". Its perfect pephyka (πέφυκα) can be likened to "fuck" and its equivalents in other Germanic languages.