Problems with such theories include a distribution that suggests a North-Sea Germanic areal form rather than an inherited one; the murkiness of the phonetic relations; and the fact that no alleged cognate outside Germanic has sexual connotations.
Although German ficken may enter the picture somehow, it is problematic in having e-grade, or umlaut, where all the others have o-grade or zero-grade of the vowel.
AHD1, following Pokorny, derived “feud”, “fey”, “fickle”, “foe”, and “fuck” from an Indo-European root peig2 = “hostile”; but AHD2 and AHD3 have dropped this connection for “fuck” and give no pre-Germanic etymon for it.
In Christianized Anglo-Saxon Britain, invading kings would require that their troops would rape the women in a common demoralization procedure.
Now, aren't you glad you learned something new today?
They would be tried and sentenced, hence you're FUCKed now etc . With precious few exceptions, words of acronymic origin date from the 20th century and no earlier.
It was said that this was a British Army charge used when soldiers were caught shagging without permission (I was never sure if it was shagging women or each other). Though a few common English words have grown out of acronyms (words created by taking the first letter(s) of major words in a phrase), ‘fuck’ isn’t one of them.
Dealing with the first of these, though it’s pleasing to think couples looking to procreate in those Dark Old Days had to first obtain the sovereign’s permission and then post a notice of what they were up to so all the neighbors could enjoy a good snicker, a moment’s thought should set that one to rest.
Were the king responsible for handing out such permissions, he wouldn’t have time to do anything else (or even to keep up with that one task).
In light of this, any claim wedded couples trying to entice the stork down their chimney were granted fornication permits crashes against the rock of the wrong word being used.