“Samhain (pronounced Sow-an) has its roots as a Gaelic festival celebrating the end of harvest season and the beginning of winter. It was celebrated on November 1, though the festivities traditionally began the night before. The Celtics would hold a huge bonfire in hopes of winning favor of the gods for a bountiful harvest the next year; and they believed it was a time when the veils thinned and the 'normal order of the Universe (was) suspended' (Samhain Wikipedia).
“Like Beltane, Samhain was a liminal or threshold festival, when the boundary between this world and the Otherworld thinned, meaning the Aos Sí (the 'spirits' or 'fairies') could more easily come into the world. Most scholars see the Aos Sí as remnants of pagan gods. At Samhain, they were appeased with offerings of food and drink, to ensure the people and their livestock survived the winter. The souls of dead kin were also thought to revisit their homes seeking hospitality, and a place was set at the table for them during a Samhain meal. Mumming and guising were part of the festival from at least the early modern era, whereby people went door-to-door in costume reciting verses in exchange for food. The costumes may have been a way of imitating, and disguising oneself from, the Aos Sí. Divination was also a big part of the festival and often involved nuts and apples. In the late 19th century John Rhys and James Frazer suggested it was the 'Celtic New Year' but that is disputed (Samhain Wikipedia).
“According to Irish mythology, Samhain (like Bealtaine) was a time when the 'doorways' to the Otherworld opened, allowing supernatural beings and the souls of the dead to come into our world; while Bealtaine was a summer festival for the living, Samhain 'was essentially a festival for the dead' (Samhain Wikipedia).
“Several sites in Ireland are especially linked to Samhain. Each Samhain a host of otherworldly beings was said to emerge from Oweynagat ('cave of the cats'), at Rathcroghan in County Roscommon. The Hill of Ward (or Tlachtga) in County Meath is thought to have been the site of a great Samhain gathering and bonfire... (Samhain Wikipedia).
“In 609, Pope Boniface IV endorsed 13 May as a Catholic holy day commemorating all Christian martyrs. J. Hennig argues that by 800, there is evidence that churches in Ireland, Northumbria (England) and Bavaria (Germany) were holding a feast commemorating all saints on 1 November, which became All Saints' Day. Alcuin of Northumbria commended his friend Arno of Salzburg, Bavaria for holding the feast on this date. James Frazer suggests this date was a Celtic idea (being the date of Samhain), while Ronald Hutton suggests it was a Germanic idea, writing that the Irish church commemorated all saints on 20 April. Some manuscripts of the Irish Martyrology of Tallaght and Martyrology of Óengus, which date to this time, have a commemoration of all saints 'of Europe' on 20 April, but a commemoration of all saints of the world on 1 November. Some have suggested that Alcuin could have used his influence with Charlemagne to introduce an Irish-Northumbrian Feast of All Saints to the Frankish Empire. In 835, the 1 November date was officially adopted in the Frankish Empire, at the behest of Pope Gregory IV... (Samhain Wikipedia.)
“In the 11th century, 2 November became established as All Souls' Day. This created the three-day observance known as Allhallowtide: All Hallows' Eve (31 October), All Hallows' Day (1 November), and All Souls' Day (2 November)... (Samhain Wikpedia.)
“It is widely believed that many of the modern secular customs of All Hallows' Eve (Halloween) were influenced by the festival of Samhain. Other scholars argue that Samhain's influence has been exaggerated, and that All Hallows' also influenced Samhain itself.... (Samhain Wikpedia.)
“The Day of the Dead (Spanish: Día de Muertos or Día de los Muertos) is a holiday celebrated from 31st October through 2nd of November inclusive, though other days, such as 6th November, may be included depending on the locality. It originated, in part, in Mexico, where it is mostly observed, but also in other places, especially by people of Mexican heritage elsewhere. Although associated with the Western Christian Allhallowtide observances of All Hallow's Eve, All Saints' Day and All Souls' Day, it has a much less solemn tone and is portrayed as a holiday of joyful celebration rather than mourning. The multi-day holiday involves family and friends gathering to pay respects and to remember friends and family members who have died. These celebrations can take a humorous tone, as celebrants remember funny events and anecdotes about the departed (Day of the Dead Wikipedia.)
“Traditions connected with the holiday include honoring the deceased using calaveras and aztec marigold flowers known as cempazúchitl, building home altars called ofrendas with the favorite foods and beverages of the departed, and visiting graves withthese items as gifts for the deceased. The celebration is not solely focused on the dead, as it is also common to give gifts to friends such as candy sugar skulls, to share traditional pan de muerto with family and friends, and to write light-hearted and often irreverent verses in the form of mock epitaphs dedicated to living friends and acquaintances, a literary form known as calaveras litarerarias (Day of the Dead Wikipedia.)
Marking the midpoint between the solstice and equinox, the three day period inclusive of the final day of October and the first two days of November really does represent the earnest beginning of winter in many parts of the U.S., Canada and Europe—though some colder climates definitely have already been under winter's spell for weeks. It's metaphorically a time when we connect with the Spirit World before going into hibernation for the cold months ahead.