Note: The term Halloween, and its older spelling Hallowe'en, is shortened from All-hallow-even, as it is the evening before "All Hallows' Day" (also known as "All Saints' Day"). The holiday was a day of religious festivities in various northern European Pagan traditions, until Popes Gregory III and Gregory IV moved the old Christian feast of All Saints Day from May 13 to November 1. In Ireland, the name was All Hallows' Eve (often shortened to Hallow Eve), and though seldom used today, it is still a well-accepted label. The festival is also known as Samhain or Oíche Shamhna to the Irish, Calan Gaeaf to the Welsh, Allantide to the Cornish and Hop-tu-Naa to the Manx. Halloween is also called Pooky Night in some parts of Ireland, presumably named after the púca, a mischievous spirit.. (wikipedia)