Happy Samhain! Happy All Hollow's Eve!
To explore the origins of the festival we celebrate on October 31, you need to start with the Celtic Pagans of the region we now know as Ireland. They celebrated a day called Samhain on the full moon closest to November 1st every year. This was the offiicial end of the Harvest season, and time for the people of antiquity to store food for the winter. They would slaughter enough animals to provide sufficient provisions for months. There was always some confusion about how much food was needed, and the ancient druids would seek advice from the spirit world. This time of year was considered propitious for contact between the spiritual and earthly realms. The Celts would engage in divination, make sacrifices to ancestral spirits, and build huge bonfires to ward off the evil ones. If all went well, they could hope for a smooth transition through the difficult part of the yearly cycle.
An interesting role was played by a faerie creature called the "puca" (accent on the "a"). This was a shape-shifter that often appeared as a goat, an eagle or a black horse, with yellow glowing eyes. It would waylay travelers and call to people in their homes, and then snatch them up for a ride on its back. Often the farmers would leave a small portion of the crop in the fields to appease this creature. While this may sound ridiculous to the modern mind, it has left its residue on Celtic culture. Halloween is stil referred to as "Pooky Night" in some parts of Ireland.
When the Romans successfully subjugated the Celts, they merged Samhain with two of their traditional festivals- one of which honored "Pomona", the goddess of fruit trees. This is where the associations with abundance and apples were formed. Since Samhain was a time to prepare for months of scarcity and discomfort, it didn't encourage the sort of indulgence we associate with the harvest festivals of today. This influnce was only incorporated from the Roman traditions.
As Catholicism later gained wide currency, Samhain was confounded with All Saint's Day, and the resulting phenomena gained it's skeleton and skull components. Hallowmas was a time to remember with reverence the lives of the departed saints of Christendom. The reliquaries that venerated the corporeality of the saints lent themselves naturally to the imagery of mortality. It's not altogether clear whether or not the Church was consciously co-opting the pagan observation of Samhain. But whether intentional or not... these historical factors, along with the pervasive influences of commercialism in modern society, form the holiday we now observe as Halloween.
Despite its convoluted and ambiguous beginnings, Halloween seems to be growing in popularity. It is a multi-billion dollar industry, and the kick-off to the holiday buying season. A large majority of the US population participates in some type of Halloween-related activity. Outdoor decorations become larger and gaudier every year. While some conservative Christian groups bemoan its "satanic" influences, most everybody else sees it as harmless, kitschy fun. Even the Mormons have "trunk-or-treating"- whereupon they decorate the back ends of their automobiles, drive to the church parking lot, and share treats and fellowship. And if it's good enough for the Mormons... well, then...