The lucky horseshoe is a big part of Irish folklore and history (despite being typically associated with western cowboy culture). The story of Dunstan and the horseshoe is that in the 10th century, St. Dunstan (a blacksmith at the time) was visited by the devil himself. The hoofed devil asked for a horseshoe for himself. So then, Dunstan nailed a red hot horseshoe tightly on one of his hooves, and the devil howled in pain. The devil begged for Dunstan to remove it. Dunstan agreed under one condition -- the devil must respect the horseshoe and never enter any place where one was hung above the door. Because of this, people believed that the horseshoe could keep evil spirits out of their homes, and thus bring in (or keep in) good fortune.