That blankness is itself worth noting. Ireland's landscape is scattered with enclosures of various kinds, from the circular earthen raths and ringforts that once served as defended farmsteads in the early medieval period, to later ecclesiastical enclosures marking out the boundaries of an early church or burial ground. The name Killeen is a version of the Irish "cillín", which typically refers to a small church or, more specifically, to an unconsecrated burial ground used for unbaptised infants and others excluded from formal Christian burial. Whether the enclosure here relates to such a site, or to an earlier or entirely different function, is a question the surviving record does not yet answer.

Killeen as a place-name occurs throughout Ireland and almost always carries this ecclesiastical trace, suggesting that wherever it appears, some early religious activity once took place nearby. Enclosures in such contexts could mark the boundary of a monastic precinct, a secular settlement, or a sacred space whose original purpose has long since been obscured by time, land use, and the gradual flattening of earthworks under centuries of farming. In Mayo particularly, early ecclesiastical sites are often modest in scale and easy to overlook in the field, their boundaries surviving as low banks or subtle changes in vegetation rather than dramatic earthen walls.