The term refers to a type of prehistoric cooking site found in enormous numbers across Ireland, typically identified by a spread of fire-cracked stone and charcoal-blackened earth, the accumulated debris of repeated use over centuries. The usual interpretation is that water was heated by dropping stones made red-hot in a fire into a trough, then used to cook meat or, in some theories, to brew or to process hides. What survives at ground level is generally just this dark, burnt spread, its original timber trough and hearth long since gone.

The Doonasleen example is not alone in its field. A second fulacht fia lies roughly forty metres to the north-east, close enough that the two sites were almost certainly used by the same community at some point, though whether simultaneously or across different periods is difficult to say without excavation. This pairing is not unusual in the Irish landscape; fulachtaí fia are among the most common prehistoric monument types in the country, and they frequently cluster in low-lying, water-adjacent ground. The North Cork area contains numerous such sites, catalogued as part of a wider county-wide archaeological inventory. The mound at Doonasleen remains unexcavated, its grass cover preserving whatever stratigraphy lies beneath.