Very few people would think to associate Halloween with the Celtic culture of ancient Ireland, but that's exactly where the holiday has its origins. The Celtic celebration of Sanhain (pronounced sow-in) began 2,000 years ago as a way to celebrate the Celtic new year, which was on November 1.

The Celts believed that at the beginning of the new year, the lines between the living and the dead blurred. On October 31, they celebrated Sanhain, which they thought to be the day when the ghosts of the dead returned to earth, causing trouble and damaging crops. They also believed that these spirits made it easier for the Druids, Celtic priests, to see into the future and make predictions.