Oct. 31st marks All Hallows Eve or Halloween. PBS’ Multifaith Calendar explains:
Set on the eve of All Saints Day, in which all saints in the Christian tradition are celebrated, All Hallows Eve is a time to keep vigil and pray for the dead. Most of the current practices associated with All Hallows Eve, or Halloween — such as costumes, Trick or Treating and Jack O’ Lanterns — can be traced back to England and Ireland.
Ancient Celts believed that the boundary between the living and the dead dissolved on this day, and that evil spirits returned to cause sickness or damage crops, so they wore costumes and masks to copy and placate the dead.
Trick or Treating resembles the medieval practice of “souling,” in which poor people would go door to door, receiving “soul cake” (typically shortbread or pastry) in exchange for prayers for the dead.
Jack O’ Lanterns are related to the Irish legend of Stingy Jack, a greedy farmer who tricked the devil into climbing a tree and trapped him there by carving a cross into the trunk. In revenge, the devil cursed Jack and condemned him to forever walk the earth at night.