The term Halloween, originally spelled Hallowe’en, is shortened from All Hallows’ Even – e’en is a shortening of even, which is a shortening of evening. It has roots in the Celtic festival of Samhain and the Christian holy day of All Saints.
Halloween’s origins date back to the ancient Celtic festival of Samhain (pronounced sow-in). The Celts, who lived 2,000 years ago in the area that is now Ireland, the United Kingdom, and northern France, celebrated their new year on November 1 and this day marked the end of summer and the harvest and 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. On the night of October 31, they celebrated Samhain, 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.
To commemorate the event, Druids built huge sacred bonfires, where the people gathered to burn crops and animals as sacrifices to the Celtic deities.
During the celebration, the Celts wore costumes, typically consisting of animal heads and skins, and attempted to tell each other’s fortunes. When the celebration was over, they re-lit their hearth fires, which they had extinguished earlier that evening, from the sacred bonfire to help protect them during the coming winter.
By A.D. 43, Romans had conquered the majority of Celtic territory. In the course of the four hundred years that they ruled the Celtic lands, two festivals of Roman origin were combined with the traditional Celtic celebration of Samhain. The first was Feralia, a day in late October when the Romans traditionally commemorated the passing of the dead. The second was a day to honor Pomona, the Roman goddess of fruit and trees.
By the 800s, the influence of Catholic Church had spread into Celtic lands. In the seventh century, Pope Boniface IV designated November 1st All Saints’ Day, a time to honor saints and martyrs. 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 Catholic Church would make November 2nd 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.
-The History Channel