It is on one such promontory that an ancient coastal fort sits, using the sea itself as its primary defence. Promontory forts, known in Irish archaeology as cliff castles or coastal promontory forts, work on a straightforward principle. A narrow neck of land connecting a headland to the mainland is cut off by one or more earthen or stone ramparts, leaving the occupants protected on the remaining sides by sheer cliff and open water. The result is a naturally fortified enclosure that required far less labour than an inland ringfort of comparable size.

Foohagh lies on the western coast of the Burren region, where limestone pavements meet the sea with very little ceremony. Promontory forts along this coastline are generally associated with the Iron Age, though some were reused or modified in early medieval times, and the boundaries between periods of occupation can be difficult to establish without excavation. The Foohagh example is recorded as a coastal promontory fort, placing it within a category of monument found at intervals all along the western and northern seaboards of Ireland, where communities with access to the shore could exploit both the land and the sea while maintaining a defensible position. The specific history of this particular site, including any details of its ramparts, dimensions, or associated finds, remains undocumented in publicly available form.