These sites, known in Irish as cilliní (the singular is cillín), were used for centuries to inter unbaptised infants and others considered, under Catholic doctrine, ineligible for consecrated ground. They occupy a particular and melancholy position in the Irish landscape, numerous yet seldom mapped with any precision, present in almost every county but rarely marked or maintained.

The theological rationale behind cilliní rested on the doctrine of limbo, which held that souls who died without baptism could not enter heaven, and therefore could not be buried in ground blessed by the Church. In practice this meant stillborn children, infants who died before a priest could be reached, and sometimes unbaptised adults, suicides, or strangers, were interred in marginal spaces: old ringfort ditches, the edges of fields, coastal promontories, or, as here at Glendaduff, in ground that carried its own informal sanctity. The name Glendaduff, from the Irish, suggests a dark or black valley, a place already carrying a particular atmosphere in local imagination. These burials were typically unmarked, or marked only with a stone placed without inscription, and the sites were tended quietly, if at all, by families carrying grief that the official Church did not formally acknowledge.

The abolition of limbo as a formal doctrine was effectively signalled by the Vatican in 2007, but cilliní had already faded from use well before that, as attitudes to infant baptism and emergency rites changed through the twentieth century. Sites like the one at Glendaduff remain as physical traces of a long and largely private grief, modest in appearance but significant in what they represent about the distance that could exist between official religious practice and the lives, and deaths, of ordinary rural families.