Known in Irish as a ráth, a ringfort is typically a roughly circular enclosure defined by one or more earthen banks and ditches, built during the early medieval period, roughly between the fifth and twelfth centuries, and used as a farmstead or defended homestead by a family of some local standing. Ireland has tens of thousands of them, and yet each one occupies a specific patch of ground with its own particular relationship to the surrounding fields, hedgerows, and water sources.

Cassarnagh is a small townland in Clare, a county whose limestone karst landscape made it an attractive place for early settlement, with good grazing land and stone readily available for construction. The ráth form here follows a pattern common across Munster and Connacht, where the earthen rampart enclosed a domestic space, sometimes with a souterrain, an underground stone-lined passage used for storage or refuge, running beneath it. Without more detailed site records currently available, the finer points of this particular monument, its dimensions, its condition, whether any finds have been associated with it, remain to be established from archival sources.