Halloween, also known as All Hallows' Eve, has its roots in the pre-Christian Celtic Festival known as Samhain, which dates back to more than 2000 years. Halloween is an end of harvest festival, a time when people in the attires of ghosts and goblins take to the streets, scaring each other and demanding candy in the custom of trick or treat. Halloween straddles between fall and winter, plenty and paucity, and life and death. Going beyond costumes and charades, Halloween has a very rich and an intriguing history.
During the pre-Christian era, the Celtics across America, Canada, and Europe celebrated Samhain as the end of harvest festival. The Pagans celebrated this period as the spiritual New Year, and believed that this was the time one could communicate with the dead. The Pagans in the Northern Hemisphere celebrated the festival in end of October, while those in the Southern Hemisphere celebrated it in end of April when winter set in there.
Samhain became the Halloween with the birth of Christianity.
With the birth of the new world religion, Christianity, the Christian missionaries began the arduous attempt of changing the religious practices of the Celtic people.
In 601 A.D. Pope Gregory issued a famous edict converting most of the Celtic festivals, beliefs, and customs into Christian practices.
All Saints Day honouring every saint in Christianity was assigned to November 1st, with the intent of replacing Samhain
However, the plan failed, and the festival of Samhain continued to be celebrated.
The church again tried by establishing All Souls' Day on November 2nd in the 9th Century. The day was dedicated to the praying for the souls of dead people.
Thus Hallows' Eve came into existence where the traditional customs were retained and redefined giving a new guise to the festival of Samhain.
Thus people continue to celebrate Halloween, derived from Hallow Evening, by propitiating the spirits.
The costumes worn by people on this day is a practice which has roots in the belief that on this evening the souls of the dead, fairies, witches and demons roam on the streets. In fact even the practice of trick-or-treat has sprung from the idea of the antics that spirits would normally play.