Overconfidence in something.
Jack Pirogue made a bet in a bar in
Cincinnati that he would make 2 of 3 darts into the double bullseye or his friends could mail his balls to the wall. He did not make
the throws and had his ballsack cut off and nailed to the bar, coincidentally named Jack's. To this day if you go to the bar you can see a leathery dried up ballsack nailed to the wall.