The term refers to a type of prehistoric cooking site, found in enormous numbers across Ireland, typically consisting of a mound of fire-cracked stones that accumulated beside a trough or water source as hot rocks were used repeatedly to boil water. They date most commonly to the Bronze Age, though some examples extend into the early medieval period, and Ireland has tens of thousands of recorded examples, making them among the most numerous field monuments in the country.

The Kilberrihert example is modest and somewhat battered. Cattle grazing the pasture have poached the surface considerably, meaning the repeated pressure of hooves on soft ground has disturbed and compacted the archaeology. What remains is a spread of burnt material beneath a covering of grass, its original mounded profile likely reduced over centuries of agricultural use. Its proximity to the well is typical of the type; a reliable water source was essential to the whole process, and fulachtaí fia are frequently found close to springs, streams, or marshy ground.