Halloween originated from the ancient Celtic festival of Samhain, a time when people would light bonfires and wear costumes to ward off ghosts. The Celts believed that on the night of October 31st, the boundary between the living and the dead was blurred, allowing spirits to return to earth.

Samhain marked the end of the harvest season and beginning of winter or the 'darker half' of the year. It was seen as a liminal time, when the boundary between this world and the Otherworld thinned. This meant the Aos Sí, the 'spirits' or 'fairies', could more easily come into this world and were particularly active.

Halloween began as a the Festival of Samhain about 2,000 years ago. It was created as a way for the Celts to scare away ghosts and spirits. They believed around that time of the year, the wall between their realm and ours thinned.