There are two reasons for the horseshoe being considered lucky that are widely agreed upon by scholars. One, is the fact that the horse shoe is a crescent shape. The other is the fact that the horse shoe is made of iron. However, it has also been suggested that the horseshoe's luck may have something to do with its connection to the animal itself.
The crescent, is the symbol of the great goddess, or triple goddess, who is worshiped by a large number of ancient civilizations. The crescent is therefore often considered to be a protective shape. This, combined with iron, makes the horseshoe a powerful symbol. Iron, because of its strength, was thought to be a very special and even somewhat magical material. Those who were able to work it, such as black smiths, were believed to be magicians with supernatural abilities. It was believed that iron could ward off demons and witches and horseshoes were often hung on people's front doors for this reason.
The horse shoe also has seven nail holes, and seven is amongst certain cultures, considered to be a lucky number. This could have something to do with the horseshoe being lucky, or could just be a mere coincidence. It was also once believed that if a horse were shod with shoes made from the iron of a sword by which a man has been killed, the horse would be exceptionally fast and would never tire.
The most interesting possibility for the lucky horseshoe superstition is perhaps its association with the horse itself. The horse has been a beloved and sometimes even worshiped animal amongst cultures all over the world, so it would make sense that the shoe of such a magnificent animal would be valued. There is a myth amongst the English in which the horse is considered a luck-bringer, and horse-worship was common practice amongst the early Celts, Teutons, and Slavs.
