Local memory has preserved its name, Cill Mór, meaning the great church, and older accounts record that rough headstones once lay within the enclosure, suggesting this was a place of burial as much as worship. The enclosure is substantial, measuring roughly 129 metres east to west and 118 metres north to south, which puts it well above the scale of a modest local chapel site. Along its southern edge, a sunken laneway survives that may be the remnant of a fosse, a defensive or boundary ditch often dug around early ecclesiastical enclosures to define sacred ground from the secular world beyond it.

The most intriguing possibility attached to Cill Mór is its connection to Mellifont Abbey, the great Cistercian house founded in 1142 a short distance to the south-west, the first Cistercian monastery established in Ireland. A scholar named Tempest, writing in the County Louth Archaeological Journal in 1944, suggested that the Proleek enclosure may have functioned as an outlying church belonging to Mellifont, one of the satellite sites a major monastic house might maintain across its landholdings. If that identification is correct, what looks today like a quiet field enclosed by old stonework was once part of the economic and spiritual network radiating out from one of medieval Ireland's most significant religious foundations. Adding to the sense of the site's layered past, the Ordnance Survey Memoranda, compiled by surveyors in the nineteenth century, record that a cross-inscribed slab was found built into the fence along the eastern side of the enclosure, a carved stone reused as ordinary field boundary material, its original context long forgotten by the time anyone thought to write it down.