- The document discusses the origins and traditions of Halloween. It originated in ancient Celtic Britain, where the pagan Celts celebrated festivals like Samhain at the start of winter. They wore costumes and lit bonfires to ward off evil spirits on Samhain night. After the Roman invasion, the festival incorporated aspects of the Roman pomona festival. When Christianity came to Britain, the tradition was adapted into All Saints' Day. Irish immigrants later brought Halloween to North America in the 19th century.