But the surrounding area carries a name that gives the stone away: 'Móinteáin an Aifrinn', which translates roughly as the Marsh of the Mass. The boulder, measuring nearly three metres east to west and standing around 1.4 metres high, served as a mass-rock during the Penal era, and the local memory of that function has never quite dissolved into the landscape.

Mass-rocks were outdoor altars used by Catholic communities in Ireland during the seventeenth and eighteenth centuries, when Penal Laws severely restricted Catholic worship, making it illegal for priests to celebrate Mass openly. Congregations would gather in remote or concealed locations, often at a large flat-topped stone that could serve as a makeshift altar. This particular boulder has a flat area along its northern side, which would have provided the necessary surface, while the upsloping southern edge gives the stone a rough, natural formality. Partially obscured now by moss and overgrowth, and set within a level clearing among trees and bushes in what remains rough marshy grazing land, it occupies a spot that would have offered both a degree of concealment and enough open ground for a gathered community. The choice of location, close to the Douglas River and screened by vegetation, reflects the practical calculations that shaped clandestine worship across rural Ireland during that period.