Samhain marks one of the two great
doorways of the Celtic year, for the Celts divided the year into two
seasons: the light and the dark, at Beltane on May 1st and Samhain on
November 1st. Some believe that Samhain was the more important
festival, marking the beginning of a whole new cycle, just as the
Celtic day began at night. For it was understood that in dark silence
comes whisperings of new beginnings, the stirring of the seed below the
ground. Whereas Beltane welcomes in the summer with joyous celebrations
at dawn, the most magically potent time of this festival is November
Eve, the night of October 31st, known today of course, as Halloween.
Samhain (Scots Gaelic: Samhuinn) literally means “summer's end.” In Scotland and Ireland, Halloween is known as Oíche Shamhna, while in Wales it is Nos Calan Gaeaf, the eve of the winter's calend, or first. With the rise of Christianity, Samhain was changed to Hallowmas, or All Saints' Day, to commemorate the souls of the blessed dead who had been canonized that year, so the night before became popularly known as Halloween, All Hallows Eve, or Hollantide. November 2nd became All Souls Day, when prayers were to be offered to the souls of all who the departed and those who were waiting in Purgatory for entry into Heaven. Throughout the centuries, pagan and Christian beliefs intertwine in a gallimaufry of celebrations from Oct 31st through November 5th, all of which appear both to challenge the ascendancy of the dark and to revel in its mystery.
Samhain (Scots Gaelic: Samhuinn) literally means “summer's end.” In Scotland and Ireland, Halloween is known as Oíche Shamhna, while in Wales it is Nos Calan Gaeaf, the eve of the winter's calend, or first. With the rise of Christianity, Samhain was changed to Hallowmas, or All Saints' Day, to commemorate the souls of the blessed dead who had been canonized that year, so the night before became popularly known as Halloween, All Hallows Eve, or Hollantide. November 2nd became All Souls Day, when prayers were to be offered to the souls of all who the departed and those who were waiting in Purgatory for entry into Heaven. Throughout the centuries, pagan and Christian beliefs intertwine in a gallimaufry of celebrations from Oct 31st through November 5th, all of which appear both to challenge the ascendancy of the dark and to revel in its mystery.
from http://www.celticspirit.org/samhain.htm
The Celtic peoples called the time between Samhain (pronounced "SOW-in" in Ireland, SOW-een in Wales, "SAV-en" in Scotland or even "SAM-haine" in non Gaelic speaking countries) and Brigid's Day "the period of little sun." Thus, Samhain is often named the "Last Harvest" or "Summer's End".
from "A Brief History of Halloween"
http://www.witchvox.com/holidays/samhain/1031_quikhistory.html