These small, often unmarked enclosures were used for centuries to inter unbaptised infants and others considered, under Catholic doctrine, ineligible for consecrated ground. They occupy a quietly sorrowful corner of the Irish landscape, often tucked beside old ringforts, ruined churches, or field boundaries, their presence marked by little more than a scatter of small stones or a slight rise in the earth.

Cilliní were in active use from at least the medieval period through to the mid-twentieth century, their use declining only as Church attitudes and civil registration practices changed. The choice of location was rarely arbitrary. Many were sited at places already felt to carry some spiritual significance, boundaries between the human and something older. The grief attached to them was largely private, carried within families rather than publicly acknowledged, which is partly why so many of these sites remain unrecorded, unmarked, and easy to walk past without recognition. Ballymoyock is a small rural townland in Mayo, a county with a particularly dense concentration of such sites, reflecting both the depth of pre-Famine population and the persistence of the practice in the west of Ireland long after it faded elsewhere.