These small, informal burial sites were used for centuries to inter unbaptised infants, and sometimes others considered outside the bounds of formal Catholic burial, including stillborn children, women who died in childbirth, and occasionally strangers or suicides. They occupy a particular place in the Irish landscape and in the country's social memory, set apart from consecrated churchyards, often located at the edges of fields, beside ancient earthworks, or on marginal land that seemed to belong, in some quiet way, between the everyday world and whatever lay beyond it.

Cillíní were a practical response to a theological problem. Canon law historically prohibited the burial of unbaptised children in consecrated ground, on the basis that they had not been received into the Church. For rural families, the cillín offered a discreet alternative, and many such sites were used continuously from the medieval period right into the twentieth century, long after the doctrinal pressures that originally created them had begun to soften. Some were sited at pre-Christian monuments or ancient enclosures, reflecting a folk instinct to place the newly dead near ground that already carried some sense of the sacred or the liminal. The Dookinelly site in Mayo belongs to this broader tradition, though the specific history of this particular ground remains to be fully documented.