The term refers to a type of prehistoric cooking site found in enormous numbers across Ireland, typically identified by a horseshoe-shaped mound of heat-shattered stone left over from repeated use. The example at Knockskehy is slightly unusual in that its spread is rectangular rather than the classic curved form, measuring roughly 16.5 metres north to south and 13.7 metres east to west, with the individual mounds of burnt stone reaching no more than 0.85 metres in height.

The general principle behind a fulacht fia is straightforward: stones were heated in a fire, then dropped into a water-filled trough to bring it to the boil, most likely for cooking meat. Over time, the thermally cracked and discarded stones accumulated into the mounds that survive today. The site at Knockskehy has not escaped the pressures of the landscape it sits in; the mounds show signs of disturbance from turf-cutting, the long tradition of extracting peat from boggy ground for fuel. That activity has altered the surface, though enough remains to read the shape and scale of what was once here. Most fulachtaí fia date to the Bronze Age, roughly 1500 to 500 BC, though some sites were in use earlier or later, and the type is so widespread in Cork and across Munster that encountering one, even in an altered state, connects a quiet field to a pattern of activity that repeated itself thousands of times across prehistoric Ireland.