Dark and Gloomy Evening Halloween Mood. Halloween's origins can be traced back to the ancient Celtic festival known as Samhain, which was held on November 1 in contemporary calendars. It was believed that on that day, the souls of the dead returned to their homes, so people dressed in costumes and lit bonfires to ward off spirits. "Hallow" — or holy person — refers to the saints celebrated on All Saints' Day, which is November 1. The "een" part of the word is a contraction of "eve" — or evening before. So basically, Halloween is just an old-fashioned way of saying "the night before All Saints' Day" — also called Hallowmas or All Hallows' Day.