The term, sometimes translated loosely as "cooking place of the deer," refers to the horseshoe-shaped mounds of burnt and shattered stone that accumulate around ancient outdoor hearths and water troughs. The working theory, supported by experimental archaeology, is that stones were heated in a fire and then dropped into a water-filled trough to bring it rapidly to the boil, whether for cooking, bathing, or some other purpose that Bronze Age people saw no need to explain to us.

Fulachtaí fia are typically dated to the Bronze Age, roughly 2000 to 500 BC, though some sites show evidence of earlier or later use. The characteristic mound forms because the heated stones crack and fragment each time they are used, and the spent material is simply discarded to the side of the trough rather than cleared away entirely. Over centuries, this debris builds into the low, kidney-shaped earthworks that field archaeologists and sharp-eyed farmers still stumble across today, often in low-lying or marshy ground where a reliable water source would have been at hand. The townland of Carrowmacloughlin sits within a part of Mayo that contains numerous such prehistoric traces, and the presence of a fulacht fia here is consistent with the broader pattern of Bronze Age activity across the west of Ireland.