Some history for you:
One of the chief auspicious days in old Irish paganism was Samhain (pronounced "Sawin"). One that day at the end of the harvest season, it was believed, evil spirits ("fairies") would come out of holes in the ground (such as "fairy mounds") and seize ordinary humans to take them down to the underworld. In order to avoid such a fate, the humans dressed up as monstrous figures in order to cause the fairies to think the humans were their own kind.
One of the chief auspicious days in old Irish paganism was Samhain (pronounced "Sawin"). One that day at the end of the harvest season, it was believed, evil spirits ("fairies") would come out of holes in the ground (such as "fairy mounds") and seize ordinary humans to take them down to the underworld. In order to avoid such a fate, the humans dressed up as monstrous figures in order to cause the fairies to think the humans were their own kind.