Etymology of "f**k"

The other day, someone told me an acronymic etymology for "f**k", to which my response was that that was most unlikely-sounding; surely this word goes back in English to Anglo-Saxon days. So when I got home, I went to my dictionaries to check. To my surprise, the Oxfnord Dictionary of English Etymology did not have the word. The Collins Concise said it entered English from German in, surprisingly late, the sixteenth century, but gave no further details. So I went to my big first-edition OED... and was astonished to discover that the word was not included. I got a little more information from WWWebster, but it was Wikipedia that finally gave me the information I was looking for, including that it only finally appeared in the OED in 1972. *boggle*