What are the origins of Halloween?

While many Americans see innocent costumes and commercialized fun, the history of Halloween is rooted in something far more pointed and pagan. This video examines how the festival of Samhain, a time when Celts believed the dead could walk among the living and barriers to the supernatural were broken, evolved. See how these ancient customs, mixed with beliefs about ghosts, witches, and witchcraft, became All Hallows' Eve, and how Satan has subtly focused this modern holiday on the ugly and demonic.

Source: www.gotquestions.org/Halloween-origin.html