Where the more familiar earthen ringfort was raised by piling and compressing soil into a circular enclosure, a cashel was constructed by stacking unmortared stone, a technique well suited to the rocky, cleared landscapes of the west of Ireland. These structures date broadly to the early medieval period, roughly the fifth to twelfth centuries, and served as farmsteads or defended homesteads for a single family or small community. They are scattered across Kerry in considerable numbers, yet each one occupies its patch of ground with a particular quiet authority, the stones still holding their positions after well over a thousand years.

The specific details of this cashel at An Fearann Iarthach are documented in the Archaeological Inventory of County Kerry, with the fuller descriptive account appearing in O'Sullivan and Sheehan's 1996 survey of South-West Kerry. That volume remains the principal reference for the early medieval and prehistoric monuments of this part of the peninsula, cataloguing hundreds of sites across a landscape that preserves an unusually dense concentration of archaeological remains. Kerry's relative geographic isolation, combined with the durability of stone construction, has meant that features like this cashel survived where earthworks elsewhere were levelled by later agriculture or development.