The term refers to a type of prehistoric cooking site found in enormous numbers across Ireland, typically consisting of a mound of fire-cracked and burnt stones built up beside a trough that would have been filled with water and heated by dropping stones directly into it. They date broadly to the Bronze Age, though the tradition persisted across a long span of prehistory, and they tend to cluster near water sources. What makes the Sallypark example quietly telling is how little is now visible above ground: the site survives mainly as a soilmark, the kind of dark staining that centuries of organic material, charcoal, and ash leave behind in the earth long after any surface mound has been levelled or dispersed.

When the field was ploughed at some point in living memory, burnt stones came to the surface, which is how sites of this kind often make themselves known again after millennia of obscurity. The discolouration of the soil is also visible in aerial photography, where the contrast between the dark spread and the surrounding pasture gives a clear outline of the feature's extent. That combination, ploughed-up burnt stone and a soilmark readable from the air, is entirely typical of fulachtaí fia that have lost their mounded profile to agriculture but retain their subsurface signature more or less intact.