To the ancient Celts, May Day was a critical time when the boundaries between the human and supernatural worlds were removed and people needed to take special measures to protect themselves against enchantments. The Beltane fire festival originated in a spring ritual in which cattle were herded between two huge bonfires to protect them from evil and disease. The earliest known mention of Beltane (formerly spelled beltene,belltaine, and beltine) is in an Old Irish dictionary commonly attributed to Cormac, a king and bishop who lived in Cashel, Ireland, toward the end of the first millennium. The Beltane spelling entered English in the 15th century by way of Scottish Gaelic.
Word History
Etymology
Middle English (Scots), May 1 or 2, from Scottish Gaelic bealltain