The line that contains fuck reads Non sunt in coeli, quia gxddbov xxkxzt pg ifmk.
Deciphering the phrase "gxddbou xxkxzt pg ifmk", here by replacing each letter by the previous letter in alphabetical order, as the English alphabet was then, yields the macaronic non sunt in coeli, quia fuccant vvivys of heli, which translated means, "They are not in heaven, because they fuck the women of Ely".
Some of these urban legends are that the word fuck came from Irish law.
If a couple were caught committing adultery, they would be punished "For Unlawful Carnal Knowledge In the Nude," with "FUCKIN" written on the stocks above them to denote the crime.
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.
There are several urban-legend false etymologies postulating an acronymic origin for the word.
A similar variant on this theory involves the recording by church clerks of the crime of "Forbidden Use of Carnal Knowledge." Another theory is that of a royal permission.
During the Black Death in the Middle Ages, towns were trying to control populations and their interactions.
Since uncontaminated resources were scarce, supposedly many towns required permission to have children.
Hence, the legend goes, that couples that were having children were required to first obtain royal permission (usually from a local magistrate or lord) and then place a sign somewhere visible from the road in their home that said "Fornicating Under Consent of King," which was later shortened to "FUCK." This story is hard to document, but has persisted in oral and literary traditions for many years; however, it has been demonstrated to be an urban legend.
In modern usage, the term fuck and its derivatives (such as fucker and fucking) can be used as a noun, a verb, an adjective, an interjection, or an adverb.