Flen is a Municipality in Södermanland County, in central Sweden. The municipality covers an area of 718.1 km². Of the total population of 16565, 8303 are male, and 8262 are female. The population density of the community is 23 inhabitants per km².
Flen flyys is a poem, written some time before 1500, that is chiefly famous for containing the first known written usage in English of the vulgar verb "fuck".
In fact the usage was "fuccant", a hybrid of an English root with a Latin conjugation, and was disguised in the text by a simple code, in which each letter was replaced with the next letter in the alphabet.
The famous line reads "Non sunt in coeli, quia gxddbov xxkxzt pg ifmk." meaning "They [the friars] are not in heaven, since..." followed by words that when decoded, taking in account the alphabet of the time, read "fvccant vvivys of heli", a Latin/English mix that means "...they fuck the wives of Ely" [a town].