A simple derogatory term used to make fun of someone.
It's use does not specify what the person has done, simply that you are letting them know your are making fun of them
Origin is from the cartoon series " Beavis and Butthead"
(said "fark-knocker"
a) a stanky fag who smells like duckbutter b) perpetrator of a smell that lingers endlessly c) an idiot who most certainly has bread for brains.