The structure was a souterrain, an underground chamber or tunnel typically constructed during the early medieval period in Ireland, most often from dry-laid stone, and used variously for storage, refuge, or as an escape route connected to a nearby settlement. What makes this particular example quietly notable is its absence: the passage was filled in at some point in the relatively recent past, leaving no visible trace above ground.

The existence of the souterrain at Teernahila is known largely through local oral tradition rather than formal excavation or detailed recording, which places it in a category of sites that archaeology must hold loosely. It was catalogued as part of a wider survey of the Iveragh Peninsula, the broad southwestern promontory of Kerry that stretches out toward the Atlantic and contains a remarkable density of archaeological remains from many periods. The filling of the passage, the date and reasons for which are unrecorded, means that whatever the structure contained or communicated about the community that built it remains inaccessible without intervention.