A souterrain, to use the proper term, is an artificial underground structure, typically built during the early medieval period in Ireland, consisting of one or more chambers or tunnels constructed from dry-stone walling and roofed with large capstones. They are found across the country in considerable numbers, usually associated with nearby settlement sites, and their purpose has been debated for generations. Theories range from cold storage for dairy produce to places of refuge during raids, and the answer in any given case may well have been both at once.

Poulbaun itself is a small townland in Clare, a county that contains a notable concentration of early medieval archaeological remains, partly owing to the Burren's unusual capacity to preserve ancient structures in its limestone landscape. Beyond the fact of the souterrain's existence and its location, the available record for this particular site is sparse. What can be said with confidence is that souterrains in Ireland generally date to somewhere between the seventh and twelfth centuries, and that their presence in a townland is usually a strong indicator that organised agricultural settlement existed nearby during that period. The name Poulbaun itself, derived from the Irish poll bán, meaning white hole or pale hollow, may carry its own quiet suggestion of a landscape marked by openings in the ground.