A souterrain is an underground stone-lined passage or chamber, typically associated with early medieval ringforts, used variously for storage, refuge, or ventilation of domestic space. That this one survives at all is something of an accident; the ringfort, or rath, within which it once sat has been levelled, its circular earthen banks long since gone.

Raths were among the most common settlement forms in early medieval Ireland, built and occupied roughly between the sixth and twelfth centuries. When a rath is levelled, whether by agriculture, land improvement, or simple time, the above-ground evidence disappears, but the underground features sometimes persist. Here, the souterrain's approximate location has been kept in local memory rather than in the landscape itself, which gives it an oddly fragile quality. The surrounding marshy ground has likely contributed both to its preservation and to the difficulty of investigating it properly.