All Hallow's Eve began as a pre-Christian Celtic festival called Samhain. It was believed that at this time of year, the souls of those who died transitioned to the other world, allowing the ghosts of the dead to mingle with the living. To honor the dead, the Celts gathered for the sacrifice of fruits, vegetables and animals. Additionally, they lit bonfires to aid the dead's journey and keep them away from the living.
Throughout Scotland and Ireland, offerings of food and drinks were left out to placate the souls of the dead, as well as fairies, witches and demons, that were believed to be roaming from door to door. "Mumming" or "guising" were also part of the festivities and included people dressing up like these creatures and receiving food in exchange for recitation of songs or verses. Some scholars suggest that dressing in costume was an attempt by the Celts to imitate and disguise themselves from the wandering spirits of the Other World. In imitating these spirits, many people took it a step further and played pranks. This inspired some villages to hollow out turnips and beets and sometimes carving grotesque faces into them to use them as lanterns to both illuminate pranksters and ward off evil spirits.