Samhain
Old Irish, "summer's end" OCT 31 – NOV 1The last of the four Gaelic quarter days, closing the harvest and opening the dark half of the year.
Named as one of four quarter days in early Irish literature, where it marks a boundary when the otherworld was said to lie open — the source of the "thinning veil" idea still used today.
Tochmarc Emire · Serglige Con Culainn (Old Irish, medieval)Bonfires, divination games, and door-to-door guising and souling for food are recorded across Ireland, Scotland, and parts of England from the 18th and 19th centuries onward.
Antiquarian folklore collections, 1780s–1900sGardnerian Wicca adopted the name and date directly, adding a mythos in which the Horned God dies and descends, to be reborn at Yule.
Gardnerian Book of Shadows, 1950s