The "Irish-English Dictionary" published by the Irish Texts Society defines the word as follows:
Eliade's "Encyclopedia of Religion" states as follows:
"Samhain, All Hallowtide, the feast of the dead in Pagan and Christian times, signaling the close of harvest and the initiation of the winter season, lasting till May, during which troops were quartered. Fairies were imagined as particularly active at this season. From it, the half-year is reckoned. Also called Feile Moingfinne (Snow Goddess)."
The "Scottish Gaelic Dictionary" defines it as "Hallowtide. The Feast of All Souls. Sam + Fuin = end of summer." Also know as: ShadowFest, Martinmas, Old Hallowmass.
"The Eve and day of Samhain were characterized as a time when the barriers between the human and supernatural worlds were broken... Not a festival honoring any particular Celtic deity, Samhain acknowledged the entire spectrum of nonhuman forces that roamed the earth during that period."
The Celts, a tribal people who inhabited most of Western and Central Europe in the first millennium BC, were a pastoral people as opposed to an agricultural people. The end of summer was significant to them because it meant the time of year when the structure of their lives changed radically. The cattle were brought down from the summer pastures in the hills and the people were gathered into the houses for the long winter. Samhain began at sundown on October 31 and extended into the following day. On the night that ended summer and began winter, the laws of space and time were suspended, the division between the two worlds became very thin, allowing hostile supernatural forces, ghosts and spirits to wander freely. Since the fairies were abroad on this night, an offering of
food or milk was frequently left for them on the steps of the house, so the homeowner could gain the blessings of the "good folk" for the coming year. Many of the households would also leave out a "dumb supper" for the spirits of the departed.
The Celtic priests who carried out the rituals in the open air were called Druids, members of pagan orders in Britain, Ireland and Gaul. They built bonfires at sacred hilltop sites and performed rituals, often involving animal and maybe human sacrifices, to honor Pagan deities, ensuring that the sun would return after the winter and frightening away evil spirits.
Certainly tell tales of the human sacrifices of the Celts, but Nora Chadwick points out in her book "The Celts" that "it is not without interest that the Romans themselves had abolished human sacrifices not long before Caesar's time, and references to the practice among various barbarian peoples have certain overtones of self-righteousness. There is little direct archaeological evidence relevant to Celtic sacrifice."
Indeed, there is little reference to this practice in Celtic literature either. The Fomorians, a race of evil giants said to inhabit portions of Ireland before the coming of the Tuatha de Danaan, or "people of the Goddess Danu", demanded the sacrifice of 2/3 of the corn, milk, and first born children of the Fir Bolg, or human inhabitants of Ireland. The De Danaan ended this practice in the second battle of Moy Tura, which took place at the same date.