These sites, found in their thousands across Ireland, are among the most common prehistoric monuments in the country, yet their exact purpose has been debated for generations. The typical fulacht fia consists of a mound of fire-cracked stone and charcoal, usually surrounding or adjacent to a trough that was once filled with water and heated by dropping stones from a fire into it. The most widely accepted theory is that they functioned as cooking sites, though brewing, textile processing, and bathing have all been proposed.

The Killawillin example survives as little more than a spread of burnt material visible within cultivated ground, which is itself telling. Ploughing over many seasons tends to disperse and flatten such deposits, meaning that what can be seen at the surface is likely only a remnant of what was originally a more substantial mound. Fulachtaí fia generally date to the Bronze Age, roughly 1500 to 500 BC, though some Irish examples have returned earlier or later dates. The presence of one at Killawillin places this corner of Cork within a pattern of Bronze Age settlement and land use that once stretched across the entire island.