Ogham is an early medieval script, typically carved as a series of notches and lines along the edge of a stone, and these particular examples were not standing in any field or churchyard when they were found. They were functioning as structural components inside a souterrain, an underground passage or storage chamber used in early medieval Ireland, where they had been repurposed, probably centuries after their original carving, as roofing slabs and supports. The stone now known as the Coolmagort ogham stone had been placed upside down in the passage, bearing the weight of a cracked and heavier stone above it.

The souterrain came to light in 1838, when workmen building a field boundary across a slight rise in the demesne of Dunloe Castle broke through its roof. Nine slabs covered the passage, six of them bearing ogham inscriptions. Along with the stones, the workmen found a number of bones and skulls, some reportedly human. The upright stone that had been propping up its cracked neighbour carries an inscription read by the scholar R. A. S. Macalister in 1945 as CUNACENA, a personal name in the genitive case, meaning roughly "of Cunacena", in the convention typical of memorial ogham stones. In 1940, before the site was properly recorded or protected, the Office of Public Works removed all seven stones from the souterrain and re-erected them close to a nearby public road. The passage itself was then filled in, and nothing now marks where it once lay.

The stone stands 1.2 metres high and up to 0.3 metres wide, erected alongside its companions near the road in the Dunloe Castle area outside Beaufort, County Kerry. The inscription it carries has since been examined as part of the Ogham in 3D project run by the School of Celtic Studies at the Dublin Institute for Advanced Studies, which has produced detailed digital records of ogham stones across Ireland.