Two thousand years ago, the Celts, who lived in what is now Ireland, England and northern France, celebrated their new year on November 1st. On the night of October 31st—called Samhain—they believed that the ghosts of the dead returned to earth. To celebrate this event, their priests—the Druids—built huge bonfires, and people made sacrifices to the Celtic deities and wore costumes of animal heads and skins. After the Romans conquered the Celts, they combined their own festivals with Samhain, one of which honored their goddess of fruit and trees. This is probably where the tradition of bobbing for apples on Halloween originated. By the 800s, Christianity had spread into Celtic lands, and the Pope designated November 1st as All Saints Day or All-hallows. October 31st became known as All-hallows Eve. Like Samhain, it was celebrated with bonfires, parades, and dressing up as saints, angels and devils.
By the time Europeans brought All-hallows Eve to North America, it had become known as Halloween. But the holiday didn’t become widely celebrated until the potato famine of 1846 forced millions of Irish immigrants to this continent. That’s when going door to door in costume asking for food or money became a popular tradition.