The one at Toorard in County Mayo belongs to a class of site known in Irish as fulacht fiadh, a term loosely meaning cooking pit of the wild. The typical form is a kidney-shaped or horseshoe mound of fire-cracked stone and charcoal-rich soil, built up over repeated use beside a water source. The theory most archaeologists favour is that stones were heated in a fire, then dropped into a water-filled trough to bring it to the boil, whether for cooking, bathing, or some other purpose that left no written record. The mystery is part of what makes these sites so quietly compelling.

Burnt mounds date broadly to the Bronze Age, roughly 2000 to 500 BC, though some sites show evidence of use across longer periods. They tend to cluster near streams, springs, or boggy ground, and Mayo, with its wet landscape and extensive peatland, preserves a significant number of them. The mounds survive largely because their contents, shattered heat-fractured stone, are of no practical use to later farmers and so were left largely undisturbed. What looks like an unremarkable hummock in a field is often the accumulated waste of dozens or hundreds of separate heating episodes carried out over generations.