Once upon a time, Halloween was different than the holiday we know it to be. Costumes were involved, but parents didn't send their kids out begging their neighbors for candy. Rumor has it that Halloween has its roots in the ancient Celtic festival of Samhain.
The Celts, who lived about 2,000 years ago in the areas of Ireland, the UK, and northern France, celebrated their new year on November 1. This celebration is known as Samhain, one of four major quarter holidays in the Gaelic calendar. This symbolized the end of summer, the end of the harvest season, and the beginning of the darker portion of the year. It is the time of year associated with human death.
Samhain was thought of as the time of year when the veil betwen the realms of the living and the dead was thinnest, enabling ghosts of the dead to return to the land of the living. Not only did the Celts think this would cause trouble for their crops, but they also believed that the presence of the dead would make it difficult for Celtic priests, called Druids, to predict the future.
Bonfires were lit during Samhain festivals for animal sacrifices to appease the Celtic gods. This is where Halloween costumes come into play. People would dress up in costumes terrifying enough to ward off roaming ghosts. These costumes were made of animal heads and skins. During these bonfires, the Celts would also try to read each others fortunes, mainly regarding death and marriage. Supposedly crops like apples and nuts were used in these divination acts.
Candles would be lit and prayers would be lifted up to the soul's of the dead. The flames, smoke, and ashes from the candles and bonfires were thought to have protective and cleansing properties, and were also used for divination. In some Celtic traditions, the bonfires were a type of symbol, in that they immitated the sun and pushed back the decay and darkness of winter.
Eventually, the Roman Empire conquered Celtic territory, and over the course of several hundred years, Roman celebrations combined with Samhain to result in the tradition we know as Halloween. Feralia was one such holiday. Celebrated in October, it was a Roman holiday to commemorate the passing of the dead. The other Roman holiday was in honor of Pomona, the Roman goddess of fruit and trees, which could possibly explain the incorporation of bobbing for apples at Halloween parties.
By the 9th century, Christianity heavily influenced the formerly Celtic territory. The Church dedicated November 2 as a day to honor their dead, called All Soul's Day. Rumor has it that the church wanted to replace the pagan holiday of Samhain. All Soul's Day was also referred to as All Hallows, or All Hallowmas, which is Middle English for All Saint's Day. The night before this holiday is the traditional night of Samhain, which is how it eventually became known as All Hallows Eve, and now as Halloween.