These are among the more enigmatic objects in the Irish archaeological landscape: boulders or slabs of stone bearing one or more cup-shaped hollows, worn smooth over centuries by water, by weather, and by human hands. Their origins and precise purposes remain debated, though they are most commonly found in ecclesiastical settings and are thought to be connected with early Christian monastic life, possibly used for grinding or for ritual purposes involving the collection of rainwater, which is sometimes credited with healing properties at sites still visited today.

Killelton itself is a ruined early church site, the kind of modest, grass-floored enclosure that punctuates the Kerry landscape and speaks to the dense network of early medieval religious foundations that once threaded through the region. The presence of the bullaun within the church ruin places it in good company across Ireland, where such stones frequently occur alongside the remains of early ecclesiastical buildings, sometimes incorporated into walls, sometimes freestanding, and sometimes, as here, simply remaining in situ as the structure around them slowly gave way over generations.