The cashel at Cahergarriff is no longer visible at ground level, its stones long since absorbed or removed, yet the townland name preserves the memory of it precisely. Cathair Garbh, meaning roughly "rough stone fort", is the Irish form from which Cahergarriff derives, and that etymology is now the most tangible thing about the site.

A cashel is a type of early medieval ringfort defined by a roughly circular enclosure wall built from dry-laid stone rather than an earthen bank. They are found across Cork and Kerry in particular, often on elevated ground with open views of the surrounding farmland, which this site apparently has in abundance. Local tradition holds that this was the original fort, the cathair, that gave the townland its name, though the structure itself has vanished from the surface. What may survive underground is more interesting: the site is associated with a souterrain, an artificially constructed underground passage or chamber, typically stone-lined, that was used in the early medieval period for storage or as a place of refuge. A separate hut site lies roughly seventy metres to the north-east, suggesting this was once a small but organised settlement rather than an isolated enclosure.