A souterrain is an underground stone-lined passage or chamber, typically constructed during the early medieval period in Ireland, roughly between the sixth and twelfth centuries. They were built by hand, roofed with large capstones, and concealed beneath farmland, often in association with a nearby ringfort or settlement. Their exact purpose has long been debated, with storage of perishables, refuge during raids, and simple cool-air cellaring all proposed as explanations. The one at Berneens is, in the current state of accessible records, little more than a name on a map and a classification on a monuments list, which is itself a quietly suggestive fact.

Clare is well supplied with early medieval underground structures, and Berneens sits in a county where the karst limestone landscape made both the construction and the survival of such passages more likely than in softer ground elsewhere. The townland name itself, an anglicisation of the Irish, points to a small gap or pass, the kind of modest topographical feature that would have mattered to people organising a farmed and defended landscape over a thousand years ago. Without further excavation records or historical documentation in the public domain, the site remains one of those monuments that archaeology has noted but not yet fully described.