Centuries ago in Britain, Scotland, and Ireland, people celebrated Samhain on October 31st, which marked the end of the harvest season and the Celtic new year. Samhain was the god of the dead, and people would light bonfires to ward off evil spirits and wear costumes to avoid being possessed by souls visiting from the afterlife. With the rise of Christianity, the holiday evolved into All Saints' Day on November 1st, which is where the name Halloween comes from. Today, one of the most common Halloween traditions is trick-or-treating, which originated in Britain as children going door-to-door in costumes asking for candy.