means A U-shaped band of metal nailed to a horse's hoof to protect it, and by extension the same shape used as a good-luck charm or in the throwing game of the same name.

from A plain compound of two old Germanic words: 'horse' (Old English 'hors') and 'shoe' (Old English 'scoh'), the latter from a Proto-Germanic root meaning a covering for the foot. The thing itself spread across Europe in the early medieval period as iron-working improved, and the lucky reputation likely grew from iron being thought to ward off evil — though the charming rule about pointing the ends up to 'hold the luck' is folklore layered on much later.