These sites, known in Irish as cillíní (the singular is cillín), were informal burial grounds used for unbaptised infants, and sometimes for others considered ineligible for consecrated ground, including stillborn children, those who died by suicide, and occasionally strangers or the very poor. They occupy a particular and melancholy position in Irish social history, sitting at the intersection of Catholic doctrine, rural custom, and private grief.

For centuries, Catholic teaching held that unbaptised children could not enter heaven, and so the Church declined to bury them in consecrated cemeteries. Families, unwilling to leave their infants entirely uncommemorated, turned instead to liminal spaces: the edges of old ringforts, early medieval enclosures, cliff tops, field boundaries, and sites associated with pre-Christian or early Christian use. A cillín was not a place of shame so much as a practical and quietly defiant solution, a way of placing children in ground that was old and in some sense already sacred, even if not formally blessed. The sites are often unmarked, or marked only by small stones, and many have been lost entirely to agricultural change or development. Glenkeen's example is recorded as a monument, which suggests it survives in some identifiable form, though its precise character and condition are not currently documented in publicly available sources.