It is, in fact, the remains of a fulacht fia, a type of site found in great numbers across Ireland and dating primarily to the Bronze Age. The mound itself is composed of burnt and fire-cracked stone, the accumulated debris of repeated episodes of heating. The most widely accepted interpretation of these sites is that they functioned as outdoor cooking places: stones were heated in a nearby fire, then dropped into a water-filled trough, raising the temperature enough to boil meat. The proximity of a stream would have supplied the water, which explains why fulachtaí fia are so consistently found close to running water or marshy ground.

The site at Knocknagoun is barely discernible now, its original form softened by centuries of grass growth and the slow compression of the burnt material beneath. That slight mound is all that survives above ground, yet it represents a pattern of activity repeated across the Irish landscape during the second millennium BC and beyond. Hundreds of similar sites have been recorded in County Cork alone, making them among the most common field monuments in the county, though their very ordinariness means they rarely attract much attention. Some researchers have argued that fulachtaí fia served social or ritual purposes in addition to, or instead of, straightforward cooking, though the debate remains open. What is clear is that whoever used the Knocknagoun site returned to it often enough to generate a mound of discarded stone large enough to still be traceable today.