Beneath or within the earthworks of a ringfort, a souterrain is said to exist, yet no trace of it can be detected on the surface. A souterrain is an underground stone-lined passage or chamber, typically built during the early medieval period and associated with ringforts across Ireland. They served various purposes, most likely as places of refuge, cool storage, or concealment. At Cahermore, even the ringfort itself leaves only a faint imprint on the landscape, and the souterrain beneath it has retreated further still, into pure tradition.

The record of this site rests on a single local source, O'Donoghue, writing in 1986, who noted the tradition of a souterrain here. That word, tradition, does a lot of work. It places the knowledge somewhere between living memory and folklore, suggesting that people in the area understood something to be underfoot, even if the physical evidence had long since become unreadable. The ringfort with which the souterrain is associated is a catalogued site in its own right, but the underground structure itself leaves no mark that survey or observation has been able to confirm.