It is a rath, the Irish term for a ringfort, and ringforts are among the most numerous archaeological monuments in Ireland, with estimates running to around 45,000 surviving examples across the island. Most date from the early medieval period, roughly the fifth to the twelfth centuries, and they served primarily as enclosed farmsteads, the raised earthen banks and ditches protecting a family's home, livestock, and stores rather than functioning as military fortifications in any grand sense.

Carrownakilly itself is a townland name with roots in Irish, and Clare as a county is dense with early medieval settlement evidence, its limestone landscape preserving earthworks that might have been ploughed flat elsewhere. A rath of this kind would typically consist of one or more concentric circular banks, known as a univallate or multivallate fort depending on the number of enclosing rings, thrown up from the material dug out of an accompanying fosse, or ditch. Inside, a farming family would have kept their house, probably a timber or wattle structure, and their animals at night. In folklore, ringforts became associated with the sí, the fairy mounds, and many survived destruction precisely because local people were reluctant to disturb them.

The specific details of this particular earthwork, its dimensions, its condition, the number of its banks, and any features recorded within it, remain sparse in what is currently available. What can be said is that its survival into the present, named and catalogued on the townland of Carrownakilly, places it within a long continuum of early Irish rural life that Clare's landscape has quietly preserved.