Its other use, the one that gives it its name, belongs to a different kind of necessity. Mass rocks are associated with the Penal Laws, the body of legislation that from the late seventeenth century onwards restricted Catholic worship in Ireland, barring priests from celebrating Mass in any formal setting. Congregations moved outside, gathering at remote outcrops, hillsides, and field margins where a flat-topped or prominent rock could serve as an improvised altar. The practice required concealment as much as convenience, and the landscape of West Cork, with its folds and valleys, offered plenty of both.

This particular outcrop sits at the terminus of the valley, a natural gathering point sheltered by the surrounding topography. The U-shape of the valley itself is a glacial form, carved by ice rather than water, and the slight rise on which the rock sits would have made it visible to an approaching congregation while remaining unobtrusive from a distance. The local tradition attaching the name 'mass rock' to the site preserves the memory of that clandestine liturgical use, even as the outcrop has long since returned to the quieter business of sheltering animals.