Where did Halloween really come from?
During the protestant reformations the leaders of the new churches used ridicule and mockery of the then Christian faith (Catholicism of today) to bolster adherents to the new religion. During the first 1500 years of the Christian religion, All Souls Day was one of the major feasts of the church. All Souls Day was a time of communion both spiritual and physical between the realm of the world and the saints of heaven. Protestants began to mock this feast day with the concept of Halloween - which became a day when protestants made fun of the Catholics with visions of ghouls and ghosts. As the new feast of mocking grew in popularity the celebration grew to include the food and decoration of other feasts of the season such as the old traditional fall and/or harvest festivals of the local regions (such as October-fest in Germany). As the protestant movement expanded, a puritan under tone took hold. Puritans believed the Christmas feast to be based in the pagan rituals of Sol-Invictus (return of the Sun) which most Sun Worshiping religions of the European community held to. As protestant Christians lost a winter feast they began to move some of the joyful celebration to Halloween as the new Protestant churches accepted their members celebrating a holiday that ridiculed the Catholic beliefs. As such fancy dress (costumes) where moved from the European Christmas to Halloween as was the English Christmas of treats became Halloween's trick-ir-treat.
In short, Halloween was created by protestants to mock Catholics; began to borrow pagan harvest festival decorations and foods; grew in stature as Puritans banned Christmas celebrations; and latter incorporated versions of European Christmas celebrations.