Ogham is an Early Medieval alphabet used primarily to write the Old Irish language, and the Brythonic languages. Ogham is sometimes called the “Celtic Tree Alphabet”, based on a high medieval Bríatharogam tradition ascribing names of trees to the individual letters. There are roughly 400 surviving ogham inscriptions on stone monuments throughout Ireland and western Britain; the bulk of them are in the south of Ireland, in Counties Kerry, Cork and Waterford.