To a passing eye it reads as little more than a slight rise in the ground, perhaps a field clearance heap or some old farm debris. It is, in fact, the remains of a fulacht fia, one of the most common yet persistently mysterious monument types in the Irish archaeological record.

Fulachta fia are generally understood to have been ancient cooking sites, typically Bronze Age in date, where stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil. The repeated heating and sudden cooling caused the stones to crack and fragment, and over centuries of use these discarded fragments accumulated into the characteristic horseshoe-shaped or oval mounds that survive in their thousands across Ireland. The burnt and blackened material that makes up such mounds is the defining feature of the type, and the example at Killeenleagh is no different, its low profile in the grass the accumulated result of repeated use over what may have been generations. Some researchers have suggested fulachta fia served purposes beyond cooking, including textile processing or bathing, though no single explanation has won universal agreement.