The designation itself is the most information readily available: it is recorded among ecclesiastical remains, suggesting that whatever stands or once stood here held some form of religious significance, whether as a mass rock used during the Penal era, an outdoor altar associated with a ruined church, or some earlier sacred feature absorbed into local memory under a plain and functional name.

Mass rocks, to give some context to one likely possibility, were flat stones or natural outcroppings used for celebrating Catholic Mass in secret during the eighteenth century, when the Penal Laws restricted Catholic worship in Ireland. They tended to occupy remote or sheltered spots, and many were later absorbed into local placenames or oral tradition long after the legal prohibitions that gave rise to them had faded. Whether the Cappagh site fits this pattern, or represents something older altogether, the name "Altar" has clearly been meaningful enough to persist in the landscape and in the documentary record.