The commercialized, creepy, zombies-lurking Halloween is a product of American capitalism that evolved with a boost from Victorian spiritualism in the mid-1800s. Its popularity has skyrocketed during the past four decades thanks to Hollywood and America’s penchant for all things ghoulish and bloody.

Thousands of years before this, however, Halloween was, at its simplest, a harvest festival in ancient Ireland. The Celtic calendar—even today—begins on November 1 with Samhain (sow-en,) meaning “end of summer.” Technically, though, it begins at nightfall on October 31 because in Celtic tradition everything moves from dark to light.

Though little is known of the original rituals, research and speculation point to bringing animals in from the pasture for winter, killing the weakest of them for winter food and harvesting fruits and vegetables for consumption and winter storage. There were also several days of feasting surrounding Samhain, and truces were called among enemy factions for determining the coming year’s direction and for peaceful games and competitions.

On October 31, “oiche shamhna” or “evening of samhain,” families extinguished the hearth fires that had burned all year and attended a community bonfire where Druids asked for protection, told fortunes, and welcomed the new year. The Celts believed that this night between the years was a supernatural time when beings from beyond could come through the thinner veils and walk the earth to communicate with the living.

To ensure protection and appease other-worldly spirits, sacrifices were made--true sacrifices, as in animals and prisoners of war, some of them live, thrown into the celebration bonfire or drowned in a nearby body of water.

As the Romans expanded their empire, cultural traditions, beliefs, and rituals deemed pagan were reconfigured or extinguished. Samhain was thus “reconfigured” and renamed to meet the Catholic Church’s standards.

All Saints Day arose out of recognizing all saints and martyrs. Originally each saint had a day of his or her own, but the numbers became so great that “All Hallows Day,” or Allhallowmas, was designated in the middle of the fourth century to honor all saints. It was celebrated in the spring until Pope Gregory III, in the mid-8th century, changed the date to November 1.

He did this, first, because there was more food available for the feasts since it was the end of harvest. Second, the Pope wanted a competitive celebration to Ireland’s Samhain. Therefore, the Irish feast of reflection and honoring the dead now had a church-sanctioned alternative—on the same day.

This is how the holiday’s name, Samhain, became All Hallow’s E’en, a.k.a. All Saint’s Evening, a.k.a. Halloween.