Halloween originated 2000 years ago in Celtic traditions where people believed ghosts returned to earth on October 31st, called Samhain. They wore costumes to avoid recognition by ghosts. Trick-or-treating began as "souling" where the poor and later children begged for food in exchange for prayers for the dead. Irish immigration in the 1800s brought Halloween traditions to America where it continues today with children wearing costumes and going door-to-door for candy instead of food and money.