A cashel is simply a ringfort built from dry-stone walling rather than earthen banks, a distinction that matters in a county like Clare where limestone lies close to the surface and timber was always scarcer than rock. These circular enclosures were the farmsteads of early medieval Ireland, typically dating from roughly the sixth to the twelfth centuries, and they are scattered across the Irish countryside in their thousands, most of them unexcavated and many still unvisited.

The particular interest of a cashel at Ballynacragga lies partly in the place-name itself. Ballynacragga derives from the Irish, most likely relating to a rocky place or a place of crags, which is consistent with the kind of exposed limestone terrain where stone-built enclosures were the practical choice for any farming family looking to define and defend their holding. The walls of a cashel would have enclosed a domestic space, perhaps a house, outbuildings, and a small yard, with the enclosure serving as much to contain livestock and mark ownership as to offer any serious military defence. In Clare, where the Burren's grey pavements give way southward to more mixed agricultural ground, cashels appear across a wide range of elevations and soil types, each one a faint signature of early medieval settlement.