Hallowe'en a contraction of "All Hallows' evening", less commonly known as Allhalloween, All Hallows' Eve, or All Saints' Eve, is a celebration observed in many countries on 31 October, the eve of the Western Christian feast of All Hallows' Day. It begins the observance of Allhallowtide, the time in the liturgical year dedicated to remembering the dead, including saints (hallows), martyrs, and all the departed.
One theory holds that many Halloween traditions were influenced by Celtic harvest festivals, particularly the Gaelic festival Samhain, which are believed to have pagan roots. Other academics believe Halloween began solely as a Christian holiday, being the vigil of All Hallow's Day. Celebrated in Ireland and Scotland for centuries, Irish and Scottish immigrants took many Halloween customs to North America in the 19th century, and then through American influence Halloween had spread to other countries by the late 20th and early 21st century.
The English word 'Halloween' comes from "All Hallows' Eve", being the evening before the Christian holy days of All Hallows' Day All Saints' Day on 1 November and All Souls' Day on 2 November. Since the time of the early Church,major feasts in Christianity (such as Christmas, Easter and Pentecost) had vigils that began the night before, as did the feast of All Hallows'. These three days are collectively called Allhallowtide and are a time when Western Christians honour all saints and pray for recently departed souls who have yet to reach Heaven.
In 4th-century Roman Edessa it was held on 13 May, and on 13 May 609, Pope Boniface IV re-dedicated the Pantheon in Rome to "St Mary and all martyrs". This was the date of Lemuria, an ancient Roman festival of the dead.
In the 8th century, Pope Gregory III (731–741) founded an oratory in St Peter's for the relics "of the holy apostles and of all saints, martyrs and confessors". Some sources say it was dedicated on 1 November, while others say it was on Palm Sunday in April 732. By 800, there is evidence that churches in Ireland and Northumbria were holding a feast commemorating all saints on 1 November. Alcuin of Northumbria, a member of Charlemagne's court, may then have introduced this 1 November date in the Frankish Empire.
In 835, it became the official date in the Frankish Empire. Some suggest this was due to Celtic influence, while others suggest it was a Germanic idea, although it is claimed that both Germanic and Celtic-speaking peoples commemorated the dead at the beginning of winter. They may have seen it as the most fitting time to do so, as it is a time of 'dying' in nature. It is also suggested the change was made on the "practical grounds that Rome in summer could not accommodate the great number of pilgrims who flocked to it", and perhaps because of public health concerns over Roman Fever, which claimed a number of lives during Rome's sultry summers.