That is about as unassuming as ruins get. But one of those walls contains a small wall-press, a shallow niche cut into the internal face, of the sort used for storing objects, and somewhere in the stonework a blocked-up opening that may once have been a doorway. The building they belonged to was rectangular, at least 17.5 metres long and probably 7 metres wide, and human bones were uncovered on its northern side during construction works at some point. Whatever this place was, it was more than a farmyard feature.

By 1836, local people were calling it Teach na gCaileachaidh Dúbha, the house of the Black Nuns, and describing it as a former nunnery. That name and that tradition were recorded in the Ordnance Survey Letters for the area. Later, the antiquarian W. G. Wood-Martin noted the doorway in the north wall when he visited in 1882, but observed that most of the building had already gone over the edge of the steep drop below, its stones lying scattered where the farmyard now sits. Scholars Gwynn and Hadcock, writing in 1970, classified the site as a Patrician monastery, meaning one associated with the early Patrician church network, which would imply considerable antiquity. The surviving masonry, however, mortared limestone rubble laid in intermittent courses, points to the late medieval period rather than anything earlier. Whether the "Black Nuns" tradition preserves a genuine memory of religious women occupying the site, or is a later folk explanation attached to mysterious ruins, cannot now be determined. The two identities, early monastery and medieval nunnery, sit alongside each other without resolution, which is perhaps the most honest thing that can be said about Carricknahorna.