A bullaun is a boulder or rock, usually of some antiquity, into which one or more cup-shaped hollows have been ground, either by human hands or, in some cases, by natural erosion. The distinction between the two is not always easy to establish, and that ambiguity is part of what makes them interesting. They appear at early Christian sites, beside holy wells, in the ruins of monasteries, and occasionally in the middle of fields with no obvious context remaining. The place name Monasternalea contains the element "monaster", from the Latin "monasterium", suggesting there was once some form of ecclesiastical settlement in the area, which would make the presence of a bullaun stone entirely consistent with the wider pattern.

Bullaun stones have attracted a great deal of folklore over the centuries. The water that collects in their hollows was commonly held to have curative properties, and the stones were sometimes used in cursing rituals, where turning a small stone within the hollow while reciting an imprecation was believed to direct harm toward an enemy. Whether these later folk practices represent a continuous tradition reaching back to the early medieval period, or whether they were layered onto older stones whose original purpose had been forgotten, is a question scholars have not fully resolved. The name of the townland itself points to a monastic past, and it is in exactly these kinds of places, where religious life once concentrated and left its physical traces, that bullaun stones most frequently survive.