The enclosure measures roughly 155 to 160 metres in diameter, and its curved line is preserved not in stone walls or earthworks easily spotted from the road, but in the boundary of Glebe land as drawn on the first-edition Ordnance Survey six-inch map. Glebe land, traditionally the portion of a parish set aside for the income of its clergyman, frequently follows the outline of much older ecclesiastical territories, and here that older shape appears to be very old indeed.

The enclosure is thought to relate to a church known as Kaiterbristelan, also rendered as Caher Breslayn, which appears in the 1302 papal taxation of the Diocese of Ardfert. That taxation document is one of the more useful surviving snapshots of medieval Irish church organisation, recording parishes and their assessed values across the diocese. The "Caher" element of the church name is significant: a caher is a stone ringfort or enclosure, and researchers have proposed that this circular boundary, still legible on nineteenth-century mapping, may be precisely the feature that gave the church its name. If so, the enclosure was already old enough and prominent enough by 1302 to serve as a landmark identifier, suggesting origins well back into the early medieval period, perhaps the first millennium.