It is a fulacht fia, a type of site found in the hundreds across Ireland, typically identified by a low mound of fire-cracked stone and charcoal left behind after repeated episodes of water heating. The basic method involved digging a trough, lining it to hold water, and then dropping stones that had been heated in a nearby fire into the water until it boiled. What the process was actually used for, whether cooking, bathing, textile preparation, or something else entirely, remains a subject of genuine debate among archaeologists.

The location at Coolaniddane fits the pattern closely. Fulachtaí fia are almost always found near water, often in low-lying or boggy ground, and the southern bank of a stream in marshy terrain is precisely the kind of setting where these sites turn up. The burnt mounds they leave behind are the accumulated debris of that stone-heating process, the discarded, heat-shattered rock building up over time into a horseshoe or kidney-shaped mound. Most examples in Ireland date to the Bronze Age, roughly 1500 to 500 BC, though some are earlier or later. The Coolaniddane site preserves that characteristic spread of burnt material, modest in description but carrying a considerable span of time in its scorched stones.