That label appeared only on the 1907 edition of the OS 6-inch map, where the feature was depicted as a dotted line running parallel with, and about five metres south-west of, a north-west to south-east field boundary. The gothic script lent it a certain gravity, the cartographic equivalent of a whispered warning. By the time anyone went to look properly, there was nothing left to see.

The earthwork sits on the ridge of a drumlin, one of the elongated oval hills formed from glacial till that give this part of Ulster its characteristic corrugated landscape. In 1955, the archaeologist Davies recorded that no archaeological feature survived at the location, which means the 1907 map may be preserving the memory of something that was already disappearing, or possibly something that was misidentified to begin with. What makes the site genuinely interesting, despite its apparent absence, is its possible connection to the Black Pig's Dyke, a series of discontinuous linear earthworks, essentially long banks and ditches, that stretch across several Ulster counties and are thought to date broadly to the Iron Age, perhaps serving as territorial boundaries or barriers controlling movement through the landscape. The Drumgristin section of the Black Pig's Dyke lies roughly 700 metres to the east-south-east, close enough to suggest that Maghernakill may once have formed part of the same system, even if the ground itself no longer holds any trace of it.