Halloween costumes are outfits worn on or around October 31, the day of Halloween. Halloween is a modern-day holiday originating in the Pagan Celtic holiday of Samhain (in Christian times, the eve of All Saints Day). Although popular histories of Halloween claim that the practice goes back to ancient celebrations of Samhain, in fact there is little primary documentation of masking or costuming on Halloween before the twentieth century. Costuming became popular for Halloween parties in America in the early 1900s, as often for adults as for children. The first mass-produced Halloween costumes appeared in stores in the 1930s when trick-or-treating was becoming popular in the United States.
What sets Halloween costumes apart from costumes for other celebrations or days of dressing up is that they are often designed to imitate supernatural and scary beings. Costumes are traditionally those of monsters such as vampires, ghosts, skeletons, witches, and devils. There are also costumes of pop culture figures like presidents, or film, television, and cartoon characters. Another popular trend is for women (and in some cases, men) to use Halloween as an excuse to wear particularly revealing costumes, showing off more skin than would be socially acceptable otherwise.