Halloween, or Hallow's Eve was the night before All Saint's day when demons were allowed one more night to roam the earth before returning to Hell.

Most Christian holidays aren't Christian to begin with. Christmas is the winter solstice-the tree comes from druid tree worship, Easter is the fertility rights of Spring deriving from the goddess Ishtar, etc..

They might have converted the heathens with the treat of burning them at the stake, but they couldn't make'm give up their parties.