That label has persisted across subsequent editions of the map, quietly passed down through revisions without further explanation or elaboration.

The most likely explanation is that the feature is a souterrain, an underground passage or chamber typically constructed during the early medieval period, often in association with ringforts. Souterrains were built from stone-lined passages or cut directly into the earth, and their precise purpose remains debated; they may have served as places of refuge, as cool storage spaces, or both. The ringfort at Knockane, recorded in the Sites and Monuments Record, provides exactly the kind of context in which a souterrain would be expected. The cartographic evidence alone does not confirm the identification, but the association is a common one across Ireland, and the designation of 'Cave' on older Ordnance Survey maps frequently turns out to reflect a souterrain entrance rather than any natural geological feature.