That semi-circular arc is not merely a quirk of local stonework. It may be the surviving outline of an Early Christian ecclesiastical enclosure, the kind of roughly circular or curvilinear boundary that defined the sacred space of an early Irish monastic or church site, typically dating to somewhere between the fifth and twelfth centuries. These enclosures often predate any standing masonry church, and their circular form reflects a pre-Norman approach to marking out consecrated ground that had more in common with the organisation of a rath, or ringfort, than with the rectilinear churchyards that followed the Anglo-Norman period.

The possibility was noted by Leo Swan in 1988, a researcher who spent considerable energy mapping such enclosures across Ireland by studying aerial photographs and field boundaries for exactly these kinds of curved, fossilised outlines. What survives at Killahugh is the graveyard wall itself, but its geometry may be preserving the memory of something considerably older than the wall's own construction, the ghost of a boundary that once defined a place of worship and perhaps of learning or burial going back well over a thousand years.