What lies beneath is the remnant of a fulacht fia, a type of prehistoric cooking or industrial site found in great numbers across Ireland, and one of the more quietly persistent puzzles in Irish archaeology. The mound itself is composed of burnt and fire-cracked stone, the accumulated debris of repeated heating and cooling cycles carried out, in most cases, during the Bronze Age.

The principle behind a fulacht fia is straightforward enough. Stones were heated in a fire and then dropped into a water-filled trough, bringing the water rapidly to the boil. The cracked and useless stones were then discarded nearby, building up over time into the horseshoe-shaped or irregular mounds that survive today. The proximity of a stream to the south-west of this site fits the pattern almost exactly, since a reliable water source was essential to the whole operation. Whether these sites were primarily used for cooking meat, processing hides, bathing, or some combination of activities is still debated, but the physical logic of the layout, fire, stone, trough, and water, is consistent across thousands of examples found throughout the island. The Lissanoohig example is barely discernible at ground level, its burnt material now thoroughly grassed over, but its presence in the pasture connects this unremarkable field to a pattern of human activity stretching back perhaps three or four thousand years.