Without adding the the demonstrations of the use of the two words in every sense except the original, the use of "fuck" as an intensifier clearly has no real sexual connotation and, in fact, it is used by some segments of society without regard to the fact that its use is still considered to be obscene. And when you are really angry, you intensify the intensifier by adding more of them to measure. There are lots of examples of this, but here's one I prepared earlier hailing, I am told, from that bastion of racial tolerance, Brixton:
"Shut the fuck up, you fuckin' fuck!"
Now that's mad.
But no one would dream, on hearing this, that there was any connection with the sexual at all.
But saying "Do you want to fuck?" is still completely and utterly unambiguously sexual. You couldn't construe it any other way. And probably, in most social circles, it's still completely unacceptable. At least as an invitation.
However, there are many more subtle ways of getting the question across without causing quite as much offence. You can take another approach, accredited to the Australian male as the normal approach to foreplay in the marriage bed, which consists of an action and a question, each on their own unexceptional, but together ...
The typical male will, if desirous of consummation, nudge his sweetheart and ask "You awake?"
- Pfranz
