A cashel is simply a ringfort constructed from stone rather than earthen banks, the choice of material usually dictated by what the local ground offered most readily. In the west of Ireland, where rock breaks through thin soils with little persuasion, stone was often the obvious answer. These enclosures were typically farmsteads of the early medieval period, roughly the fifth to twelfth centuries, protecting a family's dwelling, livestock, and status within a community that measured security in solid walls.

Beyond its classification and its location in Mayo, the specific history of this particular cashel remains to be fully documented in the public record. What can be said with confidence is that ringforts of this type are among the most numerous archaeological monument categories in Ireland, with estimates running to tens of thousands of surviving examples across the country. That abundance does not diminish any individual site so much as suggest how thoroughly this form of settlement shaped the early medieval Irish countryside. Each one represents a family, a holding, a small centre of daily life in a period before towns, before parishes as we now understand them, before most of the place-names on the modern map had taken their current form. Coolnafarna itself carries an Irish name, and the cashel almost certainly predates it.