That label, appearing on the second edition of the OS map, is a small reminder of how surveyors once reached for the nearest legible word when confronted with something older and harder to classify.

What lies behind that boulder is a souterrain, a type of man-made underground structure built during the early medieval period in Ireland, typically consisting of one or more dry-stone lined passages or chambers dug into the earth. Souterrains were associated with ringforts and enclosed settlements, and were used variously for storage, refuge, or ventilation of adjoining structures. The Kilnabrack example sits midway along an enclosing wall, a position that suggests it was integral to whatever settlement once occupied this ground. The Iveragh Peninsula, running westward into the Atlantic in south Kerry, is unusually dense with early medieval archaeology, and surveys of the area have documented souterrains, ringforts, and field systems across the landscape in considerable number.