Wikipedia, has a great article on Halloween that you can visit at http://en.wikipedia.org/wiki/Halloween#History with the proper footnotes. I've taken the liberty of copying much of their article below to share with you during this spooky, but fun, season.
"Halloween or Hallowe'en (a contraction of "All Hallows' Evening") also known as Allhalloween, All Hallows' Eve, or All Saints' Eve,) is a yearly celebration observed in a number of countries on 31 October, the eve of the Western Christian feast of All Hallows' Day. It initiates the triduum (three days) of Allhallowtide, the time in the liturgical year dedicated to remembering the dead, including saints (hallows), martyrs, and all the faithful departed believers. Within Allhallowtide, the traditional focus of All Hallows' Eve revolves around the theme of using "humor and ridicule to confront the power of death."
According to many scholars, All Hallows' Eve is a Christianized feast initially influenced by Celtic harvest festivals, with possible pagan roots from the Gaelic Samhain. Other scholars maintain that it originated independently of Samhain and has solely Christian roots.
Historian Nicholas Rogers, exploring the origins of Halloween, notes that while "some folklorists have detected its origins in the Roman feast of Pomona, the goddess of fruits and seeds, or in the festival of the dead called Parentalia, it is more typically linked to the Celtic festival of Samhain", which comes from the Old Irish for "summer's end". Samhain (pronounced sah-win or sow-in) was the first and most important of the four quarter days in the medieval Gaelic calendar and was celebrated in Ireland, Scotland and the Isle of Man. It was held on or about 31 October – 1 November and kindred festivals were held at the same time of year by the Brittonic Celts; for example Calan Gaeaf (in Wales), Kalan Gwav (in Cornwall) and Kalan Goañv (in Brittany). Samhain and Calan Gaeaf are mentioned in some of the earliest Irish and Welsh literature. The names have been used by historians to refer to Celtic Halloween customs up until the 19th century, and are still the Gaelic and Welsh names for Halloween.
Samhain/Calan Gaeaf marked the end of the harvest season and beginning of winter or the 'darker half' of the year. Like Beltane/Calan Mai, it was seen as a liminal time, when the spirits or fairies (the Aos Sí) could more easily come into our world and were particularly active. Most scholars see the Aos Sí as "degraded versions of ancient gods [...] whose power remained active in the people's minds even after they had been officially replaced by later religious beliefs". The Aos Sí were both respected and feared, with individuals often invoking the protection of God when approaching their dwellings. At Samhain, it was believed that the Aos Sí needed to be propitiated (pleased through offerings or deeds) to ensure that the people and their livestock survived the winter. Offerings of food and drink, or portions of the crops, were left for the Aos Sí. The souls of the dead were also said to revisit their homes. Places were set at the dinner table or by the fire to welcome them. The belief that the souls of the dead return home on one night or day of the year seems to have ancient origins and is found in many cultures throughout the world.
In 19th century Ireland, "candles would be lit and prayers formally offered for the souls of the dead. After this the eating, drinking, and games would begin". Throughout the Gaelic and Welsh regions, the household festivities included rituals and games intended to divine one's future, especially regarding death and marriage. Nuts and apples were often used in these divination rituals. Special bonfires were lit and there were rituals involving them. Their flames, smoke and ashes were deemed to have protective and cleansing powers, and were also used for divination. It is suggested that the fires were a kind of imitative or sympathetic magic – they mimicked the Sun, helping the "powers of growth" and holding back the decay and darkness of winter. Christian minister Eddie J. Smith suggests that the bonfires were also used to scare witches of "their awaiting punishment in hell".
In modern Ireland, Scotland, Mann and Wales, the festival included mumming and guising, the latter of which goes back at least as far as the 16th century. This involved people going house-to-house in costume (or in disguise), usually reciting verses or songs in exchange for food. It may have come from the Christian custom of souling (see below) or it may have a Gaelic folk origin, with the costumes being a means of imitating, or disguising oneself from, the Aos Sí. In Scotland, youths went house-to-house on 31 October with masked, painted or blackened faces, often threatening to do mischief if they were not welcomed. F. Marian McNeill suggests the ancient festival included people in costume representing the spirits, and that faces were marked (or blackened) with ashes taken from the sacred bonfire. In parts of Wales, men went about dressed as fearsome beings called gwrachod. In the late 19th and early 20th century, young people in Glamorgan and Orkney dressed as the opposite gender. In parts of southern Ireland, the guisers included a hobby horse. A man dressed as a Láir Bhán (white mare) led youths house-to-house reciting verses—some of which had pagan overtones—in exchange for food. If the household donated food it could expect good fortune from the 'Muck Olla'; not doing so would bring misfortune. Elsewhere in Europe, mumming and hobby horses were part of other yearly festivals. However, in the Celtic-speaking regions they were "particularly appropriate to a night upon which supernatural beings were said to be abroad and could be imitated or warded off by human wanderers"
As early as the 18th century, "imitating malignant spirits" led to playing pranks in Ireland and the Scottish Highlands. Wearing costumes at Halloween spread to England in the 20th century, as did the custom of playing pranks. The "traditional illumination for guisers or pranksters abroad on the night in some places was provided by turnips or mangel wurzels, hollowed out to act as lanterns and often carved with grotesque faces to represent spirits or goblins". These were common in parts of Ireland and the Scottish Highlands in the 19th century, as well as in Somerset (see Punkie Night). In the 20th century they spread to other parts of England and became generally known as jack-o'-lanterns."
For some videos and other information, visit:
http://www.history.com/topics/halloween
