The word and where it came from, I have honestly not the slightest clue. It is used mostly used depreciative in "Hoit die Papen!" or, as our friends from the US would say: "Shut the f*ck up!"
The long form of Papn it is Papalatur. As I don't know the roots of the word, I also have no idea what was first, but I can take an educated (you know, I am learned Austrian) guess: First Papen was used and then it was latinized to sound more educated. Just like pig-Latin is.
Homework: Earlier today I told you to get up and enjoy nature. Maybe you should try to enjoy the silence. But I know most people are unable to.