Various historians have traced Halloween to a number of pre-Christian sources. My own belief is that its origin is in the Celtic feast of Samhain (pronounced soween, with the stress on the last syllable. Well, thatís the Celts for you). It was the festival to mark the transition to winter.

The Christians took it over, along with many other festivals, and called it Halloween, meaning the eve of All Hallows, or All Souls Day. It became the day on which the Faithful were exhorted to pray for the souls of the departed. This link to the dead explains the association with ghosts, which was later extended to include witches etc.
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There never was nothing.