The stone from Monataggart, in County Cork, was one of two ogham stones discovered in just such a souterrain, where it had been pressed into service as one of the passage's upright stones, its carefully notched inscription presumably of no concern to whoever needed a sturdy slab to hold up a roof.

The discovery was recorded in 1896, and the stone, measuring roughly 0.9 metres long and 0.4 metres across, was subsequently purchased by the Royal Irish Academy and eventually incorporated into the collection of the National Museum of Ireland, where it remains today. Though broken in two, the ogham script, a writing system that uses a series of notches and strokes cut along a central stemline, running along the stone's edge was judged by the scholar R. A. S. Macalister, writing in 1945, to be entirely legible. He read the inscription as DALAGNI MAQI DALI, a formula typical of early medieval ogham commemorations: the name of an individual followed by the word for "son of" and the father's name, in this case something like "Dalagnos, son of Dalos." The names themselves belong to a period when such memorials, usually dating from roughly the fourth to the seventh centuries, were being carved across Ireland and parts of Wales and Scotland. The stone 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 uses digital scanning to document and make accessible the full corpus of surviving ogham inscriptions.