It carries a Latin inscription in what scholars describe as a debased Lombardic script, meaning a late and somewhat irregular version of the rounded, highly decorative lettering used across medieval Europe in manuscripts and stonework. The message it preserves is brief but precise: a man named Donaldus Niger O'Hea, a Friar Minor, caused this work to be made in the year of Our Lord 1454.

The Friars Minor were Franciscans, members of the mendicant order founded by Francis of Assisi in the thirteenth century, and by the fifteenth century they were well established across Munster. Ardfert itself had long been an ecclesiastical centre of some importance, associated with Saint Brendan and developed over centuries into a complex of cathedral, friary, and ancillary buildings. The plaque's Latin, rendered in the medieval convention of contracting Anno Domini to AO D, gives us a named individual at a specific moment: Donaldus Niger, whose epithet Niger simply means "the Black" or "dark", possibly referring to colouring or to a family nickname, commissioning or completing some element of the fabric in the mid-fifteenth century. The O'Hea surname connects him to a family whose presence is otherwise recorded in Munster, though the plaque itself is the detail that fixes him, briefly and concretely, to this particular wall in this particular year.