That opening leads into a souterrain, an artificially constructed underground passage or chamber, typically built during the early medieval period and used for storage, refuge, or both. The presence of such a feature so close to a caher, the Irish term for a stone-walled circular enclosure, is not unusual in itself, but what makes this site at Cahernaman quietly interesting is the cluster of remains gathered in one modest area: the outer fort, an inner ring that was probably a hut-site measuring just under fifteen metres across, and then the mound with its subterranean opening sitting a short distance away.

The relationship between these elements was recorded by a researcher identified as Ua Riain, whose observations were later compiled by A. O'Sullivan and J. Sheehan in their archaeological survey of South Kerry, published by Cork University Press in 1996. The inner ring, at roughly forty-nine feet in diameter, would have provided a defined domestic space within or beside the caher's enclosure, and the souterrain nearby would have served the community that lived there, offering cool, concealed storage for food or, in times of threat, a place to shelter. This kind of arrangement, a ringfort with associated underground structure and internal subdivisions, was common across early medieval Ireland, though each site carries its own particular configuration of features.