Lime kilns were stone-built furnaces used to burn limestone at high temperatures, producing quicklime that could then be mixed into mortar for construction. The fact that this one survives at all, even in ruin, offers a small but legible clue about how and when the structure at the centre of the same enclosure came to be built.

The kiln was constructed and put to use between 1804 and 1806, during the building of a signal tower that still stands within the enclosure. Signal towers of this period were part of a coordinated coastal defence network erected around the Irish shoreline during the Napoleonic Wars, when the threat of French invasion made rapid communication between coastal stations a military priority. The mortar needed to raise such a tower had to come from somewhere, and rather than transport processed lime over difficult terrain, builders often fired it on site. The kiln at Bunnamohaun is a direct byproduct of that pragmatic logic, a temporary piece of infrastructure that outlasted its purpose by more than two centuries.