If i'm not mistaken, 'fuck' is an angloid corruption of the German 'frick', from 'fricken', meaning "to strike". It received sexual connotations later, like so many other words.
Discussion
Wow, that's interesting! The closest modern English equivalents I can think of are "bang" and "smash", though I'm not sure how those would work in an insult. Can you use frick or fricken in a sentence?