Ancient

The ancient Celtic festival of Samhain (pronounced sow-in) is believed to be the historical origin of Halloween.

The Celts lived 2,000 years ago in the area that is now Ireland, the United Kingdom, and northern France. Their New Year, celebrated on November 1. This day marked the end of summer and the harvest. It also marked the beginning of the dark, cold winter, a time of year that was often associated with human death. Celts believed that on the night before the new year, the boundary between the worlds of the living and the dead became blurred. They celebrated Samhain on the eve of their New Year (October 31,) when it was believed that the ghosts of the dead returned to earth. In addition to causing trouble and damaging crops, Celts thought that the presence of the otherworldly spirits made it easier for the Druids, or Celtic priests, to make predictions about the future. For a people entirely dependent on the volatile natural world, these prophecies were an important source of comfort and direction during the long, dark winter.

Roots in Christianity

By the 800s, the influence of Christianity had spread into Celtic lands. In the seventh century, Pope Boniface IV designated November 1 All Saints' Day, a time to honor saints and martyrs. It is widely believed today that the pope was attempting to replace the Celtic festival of the dead with a related, but church-sanctioned holiday. The celebration was also called All-hallows or All-hallowmas (from Middle English Alholowmesse meaning All Saints' Day) and the night before it, the night of Samhain, began to be called All-hallows Eve and, eventually, Halloween. Even later, in A.D. 1000, the church would make November 2 All Souls' Day, a day to honor the dead. It was celebrated similarly to Samhain, with big bonfires, parades, and dressing up in costumes as saints, angels, and devils. Together, the three celebrations, the eve of All Saints', All Saints', and All Souls', were called Hallowmas.

European History

Halloween is also called Pooky Night in parts of Ireland, presumably named after the púca, a mischievous spirit. Many European cultural traditions hold that Halloween is one of the liminal times of the year when spirits can make contact with the physical world, and when magic is most potent (according to, for example, Catalan mythology about witches and Irish tales of the Sídhe).