The oldest known use of the F word in writing is from the 16th century (1568, possibly 1565). 
It was found in a bored student’s notes.  
Notes that he wrote during a plague quarantine.  
In his abject boredom, George Bannatyne was writing his own poetry but also copying out a famous poem called The Flyting of Dunbar and Kennedie, which is the retelling of two people shouting insults at one another. The F word comes in to play with the line “wan fukkit funling’ which roughly translates as ‘ill-f**ed foundling’.  The insult today would be something like ‘you are the product of lousy sex’.
What wondrous insults from our century are you preserving for the people of 2520?
View Bannatyne’s lovely handwriting here.