It is, in fact, the remnant of a fulacht fia, a type of prehistoric cooking site found in large numbers across Ireland, particularly in low-lying or waterlogged ground near water sources. The typical fulacht fia consisted of a trough, often timber-lined or stone-lined, filled with water that was then heated by dropping fire-cracked stones into it. The shattered, blackened stones were raked out and discarded nearby, accumulating over time into the horseshoe-shaped or kidney-shaped mounds that survive today. Thousands of these sites are known across the island, dating broadly from the Bronze Age, though their precise function has been debated; cooking is the most widely accepted explanation, though brewing, bathing, and textile processing have all been proposed.

The mound at Knockahorrea no longer has the profile it once did. According to local information, it was levelled during the 1960s, a fate that befell many such sites during the mid-twentieth century when land improvement and agricultural intensification disturbed features that had quietly endured for millennia. What remains is a scatter of burnt material across the slope, the kind of subtle archaeological trace that is easy to overlook without knowing what to look for. The stream to the east of the site would have been essential to its original function, providing the water supply that made the whole process work. That relationship between the monument and the watercourse is one of the most consistent features of fulacht fia sites across Ireland, and it is clearly visible in the layout here even in the site's reduced condition.