In the late 19th century John Rhys and James Frazer suggested it had been the 'Celtic New Year', but that is disputed. Divination was also a big part of the festival and often involved nuts and apples. The costumes may have been a way of imitating, and disguising oneself from, the Aos Sí. 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 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 meal. At Samhain, they were appeased with offerings of food and drink, to ensure the people and their livestock survived the winter. Most scholars see the Aos Sí as remnants of pagan gods. Like Beltaine, 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 our world. These were deemed to have protective and cleansing powers and there were rituals involving them. As at Beltaine, special bonfires were lit. It was when cattle were brought down from the summer pastures and when livestock were slaughtered.

The festival was not recorded in detail until the early modern era. Some of the literature also associates Samhain with bonfires and sacrifices. The early literature says Samhain was marked by great gatherings and feasts and was when the ancient burial mounds were open, which were seen as portals to the Otherworld. It is first mentioned in the earliest Irish literature, from the 9th century, and is associated with many important events in Irish mythology. Samhain is believed to have Celtic pagan origins and some Neolithic passage tombs in Ireland are aligned with the sunrise at the time of Samhain. A similar festival was held by the Brittonic Celtic people, called Calan Gaeaf in Wales, Kalan Gwav in Cornwall and Kalan Goañv in Brittany. Historically it was widely observed throughout Ireland, Scotland, Galicia and the Isle of Man (where it is spelled Sauin). It is one of the four Gaelic seasonal festivals along with Imbolc, Beltaine and Lughnasa.

This is about halfway between the autumnal equinox and winter solstice. Celebrations begin on the evening of 31 October, since the Celtic day began and ended at sunset. Samhain ( / ˈ s ɑː w ɪ n/ SAH-win, / ˈ s aʊ ɪ n/ SOW-in, Irish:, Scottish Gaelic: Manx: Sauin ) is a Gaelic festival on 1 November marking the end of the harvest season and beginning of winter or ' darker half' of the year. (or 1 May for Neopagans in the Southern hemisphere) End of the harvest season, beginning of winter

Autumn equinox meaning and celebration