Kesha mentioned it in an interview with MTV. She stated that she wrote the song about a dude who was "a total piece of shit", "a lying sack of shit" and a "giant pair". The song was originally called "Fuck You", but due to that being a popular title she renamed it. The song deals with fake orgasms and pawning diamonds he bought her.
Don't fuck with me. Out of all the bitches to fuck with. I'll write a whole album and tell somebody in an interview all about you, all the fake orgasms, tiny wieners. Don't fuck with me.