The term, loosely translated as "cooking place of the deer" or sometimes "cooking place of the wild," refers to a type of ancient outdoor cooking site, typically identified today as a low, horseshoe-shaped mound of fire-cracked stone and charcoal-dark soil. One such site sits at Kilfallinga in County Kerry, a quiet addition to the remarkable density of prehistoric remains that the county holds.

The standard explanation for fulachtaí fia is that they functioned as communal cooking sites, most likely during the Bronze Age, roughly between 1500 and 500 BC, though some examples are older. The method involved heating stones in a fire and then dropping them into a water-filled trough to bring the water rapidly to the boil. Repeated heating and sudden cooling causes the stones to crack and fragment, and it is this shattered material, accumulating over many uses, that forms the distinctive mound visible today. Experiments carried out in the twentieth century demonstrated the technique works efficiently, capable of boiling a significant volume of water in under half an hour. Some researchers have since proposed alternative uses, including brewing, hide-working, or bathing, and the debate has not fully settled. The Kilfallinga example sits within a landscape that would have seen continuous human activity from the Neolithic period onward, and Kerry's boggy, well-watered terrain is precisely the kind of environment where these sites cluster.