The custom of guising at Halloween in North America is first recorded in 1911, where a newspaper in Kingston, Ontario reported children going "guising" around the neighborhood. In 19th century America, Halloween was often celebrated with costume parades and "licentious revelries". However, efforts were made to "domesticate" the festival to conform with Victorian era morality. Halloween was made into a private rather than public holiday, celebrations involving liquor and sensuality de-emphasized, and only children were expected to celebrate the festival. Early Halloween costumes emphasized the gothic nature of Halloween, and were aimed primarily at children. Costumes were also made at home, or using items (such as make-up) which could be purchased and utilized to create a costume. But in the 1930s, A.S. Fishbach, Ben Cooper, Inc., and other firms began mass-producing Halloween costumes for sale in stores as trick-or-treating became popular in North America. Halloween costumes are often designed to imitate supernatural and scary beings. Costumes are traditionally those of monsters such as vampires, werewolves, zombies, ghosts, skeletons, witches, goblins, trolls, devils, etc. or in more recent years such science fiction-inspired characters as aliens and superheroes. There are also costumes of pop culture figures like presidents, athletes, celebrities, or characters in film, television, literature, etc. Another popular trend is for women (and in some cases, men) to use Halloween as an excuse to wear sexy or revealing costumes, showing off more skin than would be socially acceptable otherwise. Young girls also often dress as entirely non-scary characters at Halloween, including princesses, fairies, angels, cute animals and flowers.
The practice may have originated in a Celtic festival, held on 31 October–1 November, to mark the beginning of winter. It was called Samhain in Ireland, Scotland and the Isle of Man, and Calan Gaeaf in Wales, Cornwall and Brittany. The festival is believed to have pre-Christian roots. After the Christianization of Ireland in the 5th century, some of these customs may have been retained in the Christian observance of All Hallows' Eve in that region—which continued to be called Samhain/Calan Gaeaf—blending the traditions of their ancestors with Christian ones. It was seen as a liminal time, when the spirits or fairies (the Aos Sí), and the souls of the dead, could more easily come into our world. It was believed that the Aos Sí needed to be propitiated to ensure that the people and their livestock survived the winter.