Trick-or-treating may well have originated in the old custom of “souling,” as people went from house to house, begging (“mumming”) for “soul cakes,” actually prayers — in sweet form.  Sir James George Frazer wrote about this practice in The Golden Bough: a Study in Magic and Religion, a classic in anthropology, first published in 1890: … More Saints, Souls, and Haints: More Soul Cakes