What looks, at a glance, like agricultural debris is almost certainly something far older: a fulacht fia, the remains of a prehistoric cooking or processing site. These features, found in their thousands across Ireland, typically consist of a trough dug into the ground, a hearth for heating stones, and the accumulated mound of discarded burnt material that builds up over repeated use. The stones, cracked by the cycle of heating and plunging into water, were thrown aside after each use, gradually forming the distinctive horseshoe-shaped mounds that survive across the Irish landscape.

At this particular site, a slight mound, just 0.3 metres high, persists on the eastern side, and the ground to the west remains waterlogged, which is characteristic of these sites. Fulachtaí fia are almost invariably found near water or in low-lying, boggy ground, since the whole process depended on access to a reliable water source. The accepted date range for most examples runs through the Bronze Age, roughly 1500 to 500 BC, though some sites have produced earlier or later dates. The exact function of fulachtaí fia has been debated: cooking is the most widely accepted interpretation, supported by experimental archaeology, but brewing, textile processing, and hide-working have all been proposed as alternatives or additional uses. At Knockanenacrohy, the site sits in what is now agricultural land, and ploughing has disturbed but not entirely erased the spread of material that marks where fires were lit and stones were shattered, probably on many separate occasions across a considerable span of time.