Halloween, Celtic holiday Christianized before the first millenium
Halloween? An American holiday, how is this relevant with European?! A celebration inspired by the demon, a celebration of Satan trying to overturn our “cool traditions” like the All Saints' Day and the All Souls' Day. Stop! We heard too many times these angry reactions by conservative people poorly informed about and it's time to make things clear.
Hallowen is All Hallows Eve in Irland
First misunderstanding to dispel: Halloween origins are Irish, not American. The term Halloween (in Irish Hallow E’en) derive fromt he contraction of “All Hallows’ Eve”.
Since “Hallow” is the word in ancient English that means saint, Halloween means exactly “All Saint's Eve”, i.e. All Saint's Days even, surely not demon's celebration! Nontheless the Christian meaning, as is often happened in the history, has overlapped a longest tradition, Celtic in this case.
For the Celts, a people of shepherds in that days spread even in Ireland whose rhythms of life were articulated by those of the flocks, year ended at the end of October (November first was then the equivalent of our New Year's Day), with the formal ending of the werm season and the beginning of a period of darkness and cold during wich they spent time at home to build tools and to tell legends in front of a fire.
During this transition from the light to the darkness, from warm to cold, from the old to the new year, was celebrated the Samhain, as confirmed by the epigraphs contained in the Coligny's calendar.
Celebration tied up to the theme of the death (and life)
The main theme of this celebration, in tune with was happening in nature, was death: indeed during the winter season the fields seem as dead, when actually life goes renewing itself underground, where traditionally the kingdom of the dead is found. Samhain became so an holiday at the same time tied to Earth, to the livestock and the cult of the dead: at Tlachtga, near the Tara's hill, was turned on a sacred campfire where the bones of the livestock butchered in honor of Samhain.
All the other fires were extinguished, then every head of the family caught the new fire from the sacred campfire. According to legend, that night Samhain gather all the spirits of the dead, living in a land of eternal youth and happiness called Tir nan Oge, and the shield of the legendary Scottish woman warrior Scáthach (who would have trained the Irish hero Cú Chulainn in the art of fighting) was lowered, shield separating the kingdom of the living from that of dead.
Even All Souls' Day is tied to Halloween
This way in that only night deads could go back to the places in which they lived and named after them were held cheerful celebrations. Please note that this idea (i.e. the dead persons can be back to visit us once a year) has never been cancelled even by Christianity, which in 835 A.C. overlapped All Saint's Day to Samhain (only from that moment associated to the demon) and about 160 yaers later (in 998 A.C.) made to follow to the celebration also the All Souls' Day (and its eve).
Once finished the celebration of Samhain, caught the sacred fire and dressed with grotesque masks, the Celts returned to their own village, having like light source lanterns made carving onions inside which they put the embers of the sacred fire.
If you think this was the beginning of the curved pumpunks of Halloween you are absolutely right, but that is not all there.
Back to their village the Celts celebrated for 3 days, disguising themselves with the skins of the sacrificed animals so to scare the spirits and to finally make them return in the kingdom of the dead.
Here again the Christianity preceding tradition remained, but transforming the celebration in a kind of gloomy off-season Carnival.