Across Ireland, settlements with this prefix tend to cluster around sites of early medieval or Norman significance, places where something older once stood and left enough of a mark that later inhabitants continued to reference it in their geography. That a church survives at Oldcastle in County Kilkenny, recorded as a monument in its own right, suggests the site has accumulated some weight of history, even if the precise details remain to be fully documented.

Kilkenny as a county has an unusually dense concentration of early ecclesiastical foundations, many of them established in the sixth and seventh centuries during the flowering of Irish monastic culture, and later reorganised under the Anglo-Norman reforms of the twelfth century. Churches in small rural townlands like Oldcastle often represent this layering, a pre-Norman foundation absorbed into a parish structure, sometimes leaving behind little more than a ruined nave, a carved stone, or the outline of an enclosing wall visible from the air. Without more specific documentation currently available for this site, it is difficult to say whether the church at Oldcastle follows that pattern or represents something more unusual.