Ogham
An early medieval Irish alphabet of strokes along an edge, now also used as a divination set.
Also: ogam, Celtic tree alphabet, Beith-Luis-Nion, tree calendar
Ogham is a script of short strokes cut along the edge of a standing stone, used for Primitive Irish from about the fourth century CE and found in Ireland, Wales, Scotland and the Isle of Man. Most inscriptions are personal names, and an Irish manuscript, the Book of Ballymote, gives the letters tree names. The idea that ogham signs form a Celtic tree calendar comes from Robert Graves's 1948 book The White Goddess, and scholars do not accept it. Even so, many modern Druids and Pagans use ogham staves or cards for divination, treating it as a modern practice built on an old script. The alphabet is also taught in schools in Ireland as part of heritage studies.