Between October 31st and November 1st, Celtic peoples used to celebrate the Samhain Festival. Back then, the festival celebrated the end of the harvesting season. After Celts’ conversion to Christianity, the festival became known as All Hallows or All Saints Eve.
During this evening, Celts believed that the spirits of the underworld were able to contact the living world. In order to make their homes safe, people turned off their hearths or fireplace, so their homes would not be comfortable for the spirits.