The smaller of the pair at Carrowmunniagh has long been known locally as the Small Fort, a name recorded as far back as 1914, when it appeared in Neary's catalogue of the area's antiquities.

A rath, in its simplest form, is a roughly circular enclosure defined by an earthen bank and a surrounding ditch, known as a fosse. These were the everyday farmsteads of early medieval Ireland, typically dating from somewhere between the fifth and twelfth centuries, used to pen livestock and mark out a family's territory as much as to offer any serious military defence. The Carrowmunniagh example is a fairly modest specimen, measuring around 40 metres in diameter, and survives in fair condition. Its bank and external fosse are still readable in the landscape, though a number of breaches in the bank are thought to be modern intrusions rather than original features or the result of centuries of slow erosion.