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.