What makes it quietly odd is the hollow worn into its upper surface, a bowl-shaped depression roughly 42 centimetres across and 20 centimetres deep, perpetually filled with water. There is no spring beneath it; a nearby resident, Gerry Clifford, confirmed as much. The stone is a bullaun, a type of ancient carved or naturally worn rock common across Ireland and often associated with early Christian sites, and it goes by several names locally: the font, the holy stone, and, most specifically, Cloghmacudda, meaning the stone of St. Carthage Mochaeda.

The stone's name ties it to a medieval church at Kiltallagh, recorded in 1871 by M. F. Cusack as having stood where the Protestant church then stood. Cusack noted a stone in its vicinity, hollowed in the shape of an inverted cone, around which people paid rounds, the traditional practice of walking a circuit in prayer at a sacred site. The name Cloch-Mochaeda, as Cusack recorded it, links the stone directly to St. Carthage Mochaeda, an early Irish saint of some significance. Folklore gathered from Castlemaine schoolchildren adds further texture. One child wrote that the ruined settlement of Clounalassan was probably connected to the father of a man named Fingen Macuda, and described how people came to the holy stone before dawn, bringing water from a nearby well, saying several rosaries, and washing their eyes in the water in the hope of a cure. Rags and tokens were left on a tree beside the stone afterwards, a widespread Irish custom at healing sites. The children's account carries a warning too: picking up someone else's rag from the tree was said to transfer their disease to you.