A cashel is a ringfort built from stone rather than earth and timber, a circular enclosure whose walls once defined a farmstead, a place of livestock and family, during Ireland's early medieval period, roughly between the fifth and twelfth centuries. Thousands of these structures survive across the country, yet each one occupies its own particular ground, shaped by whoever chose that spot, that slope, that view.

The term ringfort covers a broad family of enclosures, and the cashel variant tends to appear more frequently in areas where stone is the dominant building material close to hand, which makes its presence in the stony, drumlin-scattered terrain of south Mayo unremarkable in one sense and entirely logical in another. Aghamore itself is a small rural parish, its name derived from the Irish Achadh Mór, meaning the great field, and the land around it has been farmed continuously since long before any written record survives. The cashel would have been a working enclosure first, a defended homestead for an early Irish farming household, its thick stone walls serving as much to keep animals in as to keep threats out.