Halloween is old — much older, in fact, than the word "Halloween" itself.
Our spookiest holiday is thought to come from the ancient Celtic festival of Samhain, which marked the end of the warm seasons and ushered in the darker days of winter. The veil between the living and the dead was believed to be at its thinnest, so the Celts built bonfires to illuminate the night, shared sweet treats, and wore costumes to confuse and ward off evil spirits that surely lurked nearby.
Early Christians didn't care for pagan observances, and so in the 8th century A.D., Pope Gregory III declared that November 1 would be All Saints' Day, a day to venerate martyrs and saints, followed on November 2 by All Souls Day, a day to remember the dead. But people love a party, and despite Pope's efforts to quash the pagan rituals, the bonfires and costumes continued.
In fact, the Pope's efforts probably backfired entirely. Some historians posit that on the night before All Saints' Day, people would gather to hold vigils and pray for the dead trapped in purgatory, which may have evolved into ghost stories around the fire.
The name Halloween is courtesy of the Scots, who started calling All Hallows' Eve "Hallow-e'en" in the late 18th century, a phrase that means "saint evening" in Scottish. The Scottish poet Robert Burns did away with the extraneous punctuation entirely in 1789 with his poem "Halloween."
As with so many other American traditions, immigrants brought Halloween to our shores, where it flourished and eventually went commercial. But for decades, Halloween was much heavier on destructive tricks than treats. U.S. cities later adopted officially sanctioned trick-or-treating to curb the vandalism that, by the 1930s, had become quite costly each year.
So the next time a gaggle of kids ring your doorbell and recite "trick or treat," just remember — a hundred years ago, that familiar phrase would have been an actual threat.