The font is thought to have originated not at this church at all, but at Dunbrody Abbey, the Cistercian house some miles to the north. One of its four sides is decorated with banded ornament showing Anglo-Saxon influence, a detail that makes it an outlier in the Irish medieval landscape and connects it to a similar font surviving at Bannow church, also in County Wexford.

The church itself sits within a subrectangular graveyard in the small Hook Peninsula village of Fethard, and its origins are genuinely difficult to pin down. Written references go back to around 1200, but the site may be older still; the diocese of Ferns appears to have held claims here that pre-date the earliest Anglo-Norman grants, suggesting a pre-conquest foundation. By 1615, when Thomas Ram, Protestant bishop of Ferns, conducted a visitation, the vicar was one Richard Allen and both the church and chancel had been repaired. By 1684, however, a writer named Richard Leigh recorded it as unroofed and dedicated to St Idanas, his rendering of the early Irish saint Edan, also known as Mogue. The present building went up in the late 1830s, though the slight outward lean, or batter, of the nave walls may reflect the incorporation of earlier stonework. Scattered around the graveyard are further medieval survivals: a small cube of conglomerate stone that once formed the base of a finial-cross set atop a gable, its four faces carved with cusped ogee-headed decoration; and a graveslab bearing an incised cross with fleur-de-lys terminals and an inscription in lombardic lettering, written in French, commemorating Thomas de Ancayne, tentatively identified as Bishop Thomas Denne, who died in 1400. The lettering runs along the chamfered edge of the slab, a detail easy to miss without crouching down to look.

The church sits in close company with other medieval remains. A motte, the earthen mound at the core of a motte-and-bailey castle, lies roughly forty metres to the north, and the remains of a castle stand around forty-five metres to the north-west, placing the graveyard at the centre of what was once a concentrated medieval settlement. The valley to the east, running broadly north to south, gives the site a quietly enclosed quality that helps explain why so much has survived in one small area.