Costumed trick-or-treating takes its inspiration from the Celtic holiday Samhain—“summer’s end” in Irish—more than 2,000 years ago. Samhain marked New Year’s Day and fell around ...

Whether or not human sacrifice occurred, Samhain was a supernatural period. The Celts were a pastoral people, so winter was a lean time for them, and the end of summer meant a dramatic shift in their ...