Samhain - aka Halloween::Gaelic festival held Oct 'Samhain' is derived from Old Irish meaning "summer's end." It marked the end of the harvest and of the "lighter half" of the year and the start of the "darker half".
People have been dressing up in costume for Halloween for many years. Here is a collection of vintage photos showing Halloween costumes through the years. These costumes look a lot scarier than some of the costumes we see now.