The document discusses the origins and traditions of Halloween costumes and trick-or-treating. It suggests that the modern traditions of wearing costumes and going door-to-door collecting treats on October 31st are linked to medieval European practices of mumming and souling on the eves of All Saints' and All Souls' Days. People would wear costumes, sing, and engage in mischief-making while mumming or go door-to-door offering prayers for the dead in exchange for treats like cakes during souling. Over time, these traditions merged with the modern celebration of Halloween.