The mystery unravelled: Google Glossary: “In old England, anyone caught in illegal cohabitation was charged with ‘unlawful carnal knowledge’—that was the technical term. It was a very common offense and, on the blotter, instead of writing out that so-and-so was being held ‘for unlawful carnal knowledge’ they would just write, ‘F.U.C.K.’
No idea on when it became a ‘dirty’ word. [Adam Curry: Adam Curry’s Weblog]
No idea whether true or not, either….
[Several hours later:
At 4:54 PM -0800 12/15/02, Gautam wrote:
Sigh. And me the inveterate Snopes checker…