A souterrain is an underground stone-lined passage or chamber, typically built during the early medieval period in Ireland for storage, refuge, or concealment. What makes this particular example unusual is that it may no longer be accessible at all: local tradition holds that it was filled in at some point, and today there is no visible surface trace of anything beneath the ground.

The field where the possible souterrain lies is known locally as the 'convent field', a name that hints at some form of religious association in the area's past, though the precise connection is not recorded. What is recorded is a specific account, collected in 1938, of men actually entering an underground passage on the site. That account, preserved by Myler in 1998, places living memory of access to the passage well within the twentieth century, which makes the subsequent disappearance of any surface evidence all the more striking. Someone, at some point between that 1938 visit and the present, apparently decided the passage should be closed off, and the ground above it has since given nothing away.