These sites, known in Irish as cillíní (the singular is cillín), were used for centuries to inter unbaptised infants and others who, under Catholic doctrine, could not be buried in consecrated ground. Stillborn children, the unbaptised, and sometimes suicides or strangers were laid to rest in these liminal places, typically on the margins of parishes, beside old earthworks, or at the edges of townlands. The locations were chosen carefully, if quietly, by communities navigating the space between religious rule and a deeply human need to give their dead somewhere to belong.

Cillíní are among the more melancholy features of the Irish archaeological landscape. Their use spans from the early medieval period through to the twentieth century in some areas, persisting longest in rural and western counties where older customs held on. Mayo has a particularly high concentration of recorded sites. The grounds were rarely marked with formal headstones, and many survive today as low, grassy enclosures or barely perceptible rises in a field, recognisable mainly to those who already know what they are looking for. The absence of documentation for the Tawnagh site means its precise history, including when it was last used or how it was originally enclosed, remains unclear for now.