Though Halloween today is largely known for its commercialized customs of costumes, candy, and carved pumpkins, its origins trace back more than 2,000 years to the Celtic festival of Samhain. Celebrated by ancient Celts in the lands that are now Ireland, the United Kingdom, and northern France, Samhain marked the end of the harvest season and the beginning of the colder, darker half of the year. The Celts believed that on the night before the new year, which fell on November 1, the boundary between the worlds of the living and the dead became blurred and spirits of the deceased roamed the Earth. The rituals performed on this night were a mix of reverence and fear, intended to both honor ancestors and ward off malevolent spirits.

This ancient pagan festival laid the groundwork for many of the Halloween traditions we still recognize today. To protect themselves from the roaming ghosts, the Celts would light huge bonfires and wear costumes, often fashioned from animal hides and heads, to disguise themselves from the spirits. Offerings of food and drink were left outside homes to appease these supernatural visitors, a practice that eventually evolved into the modern custom of trick-or-treating. Over time, as Christianity spread through Celtic lands, the church adopted and transformed these pagan rites, designating November 1 as All Saints' Day. This turned the traditional night of Samhain, October 31, into All Hallows' Eve, and the folk traditions persisted, blending with the new religious holiday to create the modern Halloween.