What sets it apart is its Irish name: Carraig an Aifrinn, the rock of the Mass. That name points to a period in Irish history when Catholic worship was driven outdoors, practised in secret at informal outdoor sites scattered across the countryside, often on hillsides, in hollows, or beside natural landmarks that offered both shelter and concealment.

Mass-rocks date broadly from the era of the Penal Laws, the body of legislation enacted from the late seventeenth century onwards that severely restricted Catholic religious practice in Ireland. With church buildings closed or confiscated, priests celebrated Mass at whatever flat surface a townland could offer, frequently a conveniently shaped outcrop of stone. The rock at Lisnamoyle Otra sits on the floor of a valley carved by a small stream running roughly north-northwest to south-southeast, about seventy-five metres to the northeast of the stone itself. It faces southwest, a practical orientation that would have caught available light and faced a gathered congregation. The rock measures roughly 0.8 to 1.35 metres across and rises between 0.45 and 0.8 metres from the ground, its upper surface now tilting down toward the northeast, where a whitethorn tree has grown up around it and begun to engulf the stone. The whitethorn, also known as hawthorn, carries its own weight of folk association in Ireland, long regarded as a tree not to be disturbed, which lends this particular encroachment an unintentional resonance. The site is referenced in Ó Gallachair's 1957 study, which places it among the documented Mass-rock sites of the region.