I've checked this one out before...
'Fuck' is definitely not an acronym, it comes from Middle English- fuccant-which means "they fuck". It was first written in a poem in a mixture of Latin and English sometime before 1500.
Well, I know the finger went back to ancient Greece and Rome. One of the perverted emperors (either Nero or Caligula, I can't remember) had his subjects kiss his middle finger, as a double-entendre for you-know-what.
Hope this clears it up!