The Celts, who lived about 2000 years ago in what we now know today as the United Kingdom and Ireland, celebrated New Year on November 1st. They believed that on the night before New Year the boundary between the worlds of the living and the world of the dead became blurred. It was at this time, on the night of October 31st, when they celebrated Samhain, that the ghosts of the dead returned to earth. The Celts believed that the presence of spirits made it easier for the Druids, who were Celtic priests, to predict the future.
Samhain was celebrated with the wearing of costumes (typically made up of animal heads and skins) and prophecies of the future. They also extinguished their hearth fires and built huge bonfires, where people gathered to burn crops and offer animal sacrifices to the Celtic deities. After the ceremonies, they re-lit their hearth fires to protect them through the winter.
By A.D. 43 the Romans had conquered the bulk of the Celtic territory and during the course of the next 400 years the ritual of Samhain evolved to combine two festivals of Roman origin. One was Feralia, a day in late October when Romans commemorated the passing of the dead. The other was to honor Pomona, the Roman goddess of fruit and trees. Her symbol is the apple, which might tie in with the “bobbing” for apples tradition enjoyed by “children” of all ages at Halloween.
When the 800′s rolled around, the influence of Christianity had spread to Celtic lands. And, it is generally believed that, in the 7th century, Pope Bonafice IV attempted to replace the Samhain festival of the dead by designating November 1st as a church-sanctioned holiday labeled All Saints’ Day to honor saints and martyrs. It was also called All-hallows or All-hallowsmas.
Later on, around A.D. 1000, the second day of November was labeled All Souls’ Day to honor the dead. The All Saints Day festivity was similar to Samhain with bonfires, parades and dressing up in costumes as saints, angels and demons. The combination of all three celebrations was called Hallowmas. The eve of Samhain started to be called All-hallows eve and eventually Halloween.