That label, "fort", appeared on a revision of the Ordnance Survey six-inch map dated 1858, though the original survey of 1834 had apparently passed it by. The enclosure itself measures roughly 23 metres across on its northeast to southwest axis, with a curving field bank still traceable along the northern, eastern, and southern edges of the perimeter.

The site sits at the southern end of a short north-to-south drumlin ridge, the kind of low, oval hill shaped by glacial deposits that characterise much of the Monaghan landscape. Ringforts, known variously as raths or cashels depending on whether they were built from earthwork or stone, were the most common form of rural settlement in early medieval Ireland, typically dating from roughly the fifth to the twelfth century. Most enclosed a farmstead and its immediate outbuildings. At Cornafaghy, the surviving earthwork is modest, and what archaeology lies beneath the grass has not been excavated, so the enclosure's precise date and function remain open questions. Its appearance on the 1858 map revision rather than the 1834 original may simply reflect improvements in surveying coverage rather than any change to the feature itself.