were did the word f@#k come from and why is it so offensive?

No one is quite sure where the word arose, but it has been around for many hundreds of years. There are similar words in Latin (futuere), German (fickin) or the Norwegian (fukka).

It is unclear whether the word has always been considered vulgar, and if not, when it first started to be considered vulgar. Some evidence indicates that in some English-speaking locales it was considered acceptable as late as the 17th century meaning “to strike” or “to penetrate.” The word became increasingly offensive over time because people used it in a mean or deraguatory way.

in ancient times if you were unmarried and caught doing it you were put in the town square in like a shackle made of wood and above your head would read For Unlawful Carnal Knowledge.