A bullaun is a large stone, usually boulder-sized, into which one or more rounded depressions have been ground or worn, typically forming a shallow basin. These hollows were almost certainly functional at some point, perhaps used for grinding grain or preparing pigments, though many became associated over time with early Christian sites and the curative or cursing properties attributed to the water that collects in them. They are found all over Ireland, yet each one sits in its own particular silence, connected to a place in ways that are rarely fully recoverable.

Killaan itself is a townland whose name suggests an early ecclesiastical association, the element "kill" deriving from the Old Irish "cill", meaning a church or monastic cell. Bullaun stones are frequently found in the vicinity of such sites, sometimes incorporated into later churchyard walls, sometimes left in the open ground nearby. Whether the Killaan example retains that kind of context, or whether it has been displaced over the centuries, is the sort of detail that field observation and local knowledge would be needed to confirm.