The enclosure is a rath, a type of ringfort built in early medieval Ireland, typically as a defended farmstead surrounded by an earthen bank and ditch. This one, however, is remembered not for its original inhabitants but for the children buried within it, unbaptised infants whose deaths placed them, in the theology of the time, outside the reach of consecrated ground.

The practice of burying unbaptised babies in liminal places, old earthworks, field boundaries, shorelines, was widespread across Ireland well into the twentieth century. Catholic doctrine held that without baptism, an infant could not enter heaven, and so the Church refused these children burial in parish graveyards. Families turned instead to ancient, unconsecrated ground, and raths were a common choice, their age and otherness lending them a kind of informal sanctity. At Ballyheeragh, local tradition holds that the interior of the rath served exactly this purpose. These burial places are known in Irish as cillíní, sometimes spelled killeens, and they are found across every county, though rarely marked or acknowledged in any official way. Here, no graves are visible at the surface. The ground gives nothing away.