It seems to me people start Halloween the first of October. They claim it has overtaken Christmas as the best holiday of the year. Approximately 100 countries celebrate Halloween but just what are we actually celebrating? 

Halloween's origins date – 4000 B.C. - when according to the Celtic lunar calendar “summer’s end” was celebrated. This festival was called Samhain (Scots Gaelic: Samhuinn). Festivals were celebrated on the "eve" rather than the day, thus making October 31st the beginning of the most sacred of all holidays. The word was also used for the first month of the ancient Celtic calendar, and in particular the first three nights of that month; the festival marks the beginning of the winter season. "All Hallows’ Day", also called "All Saints’ Day", which is a Catholic day of religious observance in honor of saints, and comes from a contracted corruption of All Hallows’ Eve.  The Romans adopted these practices as their own in the first century and incorporated Samhain with their own.  Pomona, the goddess of fruits and tress was celebrated in October and she was symbolized by the apple. This might explain the tradition of bobbing for apples on Halloween. 

One story says that all on the eve of October 31, the disembodied spirits of all those who died during the preceding year would come back in search of living bodies to possess for the next year.  It was believed to be their only hope for the afterlife. The Celts believed that all laws of space and time were suspended during this time allowing the spirit world to intermingle with the living. Naturally the still-living did not want to be possessed, so on the night of October 31, villagers would extinguish the fires in their homes to make them cold and uncomfortable.  They would dress up in all manners of ghoulish costumes and noisily parade around the neighborhood, being as destructive as possible to frighten away the spirits. Probably a better explanation as to why all extinguished their fires as so that all Celtic fires could relight their fires from a common source.  The Druidic  fire that was kept burning in the middle of Ireland was at Hill of Uisneach . This festival was called Samhain (Scots Gaelic: Samhuinn). Often Druid priests would throw the bones of cattle into the flames and, hence, “bone fire” became “bonfire. 

The Jack O’Lantern probably comes from Irish folklore. As the tale is told, a man named Jack who was notorious as a drunkard and a trickster, tricked Satan into climbing a tree.  Jack then carved a cross into the trunk trapping the devil up the tree.  Jack made a deal with the devil that if he would never tempt him again, he would promise to let him down from the tree. 

According to legend, when Jack died he was denied entrance to heaven because of his evil ways but he was also denied entrance to hell because he had tricked the devil. Instead the devil gave him a single ember to light his way through the frigid darkness. The ember was place in a hollowed out turnip to keep it glowing longer. The Irish originally used turnips as their “ jack’s lanterns” . But when they came to America they found that pumpkins were far more plentiful. The custom of Halloween was brought to America in the 1840s by Irish immigrants fleeing their country's potato famine. The custom of trick-or-treating is thought not to have originated with the Celts, but from a 9^th century European custom called “souling”. On November 2, All Souls’ Day, early Christians would walk from village to village begging for “soul cakes” made out of square pieces bread with currants. The more cakes they would receive – the more prayers they would promise to say for the dead relatives of the donors. At that time, it was believed that the dead stayed in limbo for a time and that prayers, even those offered by strangers, could expedite their souls into heaven. 

Black and orange are typically associated with Halloween. Orange is a symbol of strength and endurance and, along with brown and gold, stands for the harvest and autumn. Black is typically a symbol of death and darkness and acts as a reminder that Halloween once was a festival that marked the boundaries between life and death. 

One final tidbit: "Samhainophobia" is the fear of Halloween.

Related Reading

Historian Joe McGowan Chats About Halloween Traditions in Ireland