A rath is a roughly circular ringfort, typically built during the early medieval period as a farmstead enclosed by earthen banks and ditches, and souterrains are the stone-lined underground passages sometimes found within them, used variously for storage, refuge, or both. The one at Caherdean occupies a peculiar position in the archaeological record: present enough to be listed, absent enough that nothing of it can actually be seen.

What little is known comes from a Schools Manuscript entry made in the 1940s, part of a large folklore and local knowledge collection gathered by schoolchildren across Ireland. That record noted 'an entrance' in the centre of the rath. No excavation appears to have followed, no further description was added, and the site now shows no visible remains. The cautious designation of 'possible souterrain' reflects exactly this situation: a single, decades-old observation of an opening, with nothing since to confirm or contradict it.

This kind of ambiguity is not unusual in Irish field archaeology. Many souterrains were backfilled, collapsed, or built over, leaving only a local memory or an old note as evidence of their existence. At Caherdean, even that memory is at one remove, filtered through a schoolchild's account from eighty years ago. The rath itself remains, but what it may once have concealed has left no trace above ground.