A cashel is simply a ringfort built from stone rather than earth, a circular enclosure whose thick dry-stone walls once defined the boundary of an early medieval farmstead, separating the domestic world inside from the open countryside beyond. Where earthen raths relied on banked soil and ditches, cashels used whatever stone the local geology offered, and in the rocky west of Ireland that was rarely in short supply.

Ringforts of both kinds were built primarily between roughly 500 and 1000 AD, though many remained in use or were adapted well beyond that period. They were the basic unit of rural settlement in early medieval Ireland, home to a farming family and their livestock, and their circular form was practical as much as symbolic. The cashel at Carrigeen belongs to this long tradition, a remnant of a way of organising land and life that once covered the country so densely that an estimated 40,000 or more such enclosures still survive in some form across the island.