An old celt story says that, on the 31st of November, the spirits of all those who had died along the preceding year would come back in search of living bodies to possess . It was believed to be their only hope for the afterlife. The Celts believed all laws of space and time were suspended during this time, allowing the spirit world to mix with the living. Naturally, the still-living did not want to be possessed. So on that night, villagers would extinguish the fires in their homes, to make them cold and undesirable. They would then dress up in all manner of ghoulish costumes and noisily parade around the neighborhood, being as destructive as possible in order to frighten away spirits looking for bodies to possess.
The Romans adopted the Celtic practices as their own. But in the first century AD, it was assimilated into other Roman traditions that took place in October, such as their day to honor Pomona, the Roman goddess of fruit and trees. The symbol of Pomona is the apple, which might explain the origin of our modern tradition of bobbing for apples on Halloween.
In Greek mythology, goddesses of the underworld were often used to invoke the Samhain. Popular Greek Goddess costumes portray Hecate and Medusa. Today, Hecate is often referred to as the goddess of witches.
The practices also changed over time to become more ritualized. The custom of Halloween was brought to America in the 1840's by Irish immigrants fleeing their country's potato famine.
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