Halloween was not always the observance it is today. It started as a tradition that came from the ancient Celtic festival of Samhain, when people would light bonfires and wear costumes to ward off ghosts.
The evening before was known as All Hallows Eve, and later Halloween.
The Celts, who lived 2,000 years ago, mostly in the area that is now Ireland, the United Kingdom, and northern France, celebrated their new year on November 1.
The modern-day practice of wearing a costume is said to have roots in the medieval practice of mumming, which is closely related to souling.