The castle appears on the First Edition Ordnance Survey maps, marking its location near the shoreline where the Atlantic meets this historic port town. According to Samuel Lewis’s 1837 Topographical Dictionary, the fortress was built by Dhermod McCarthy, a member of one of Munster’s most powerful Gaelic families who controlled much of southwest Ireland during the medieval period.

The McCarthy clan, particularly the MacCarthy Reagh branch, held sway over this region for centuries, building castles and tower houses to defend their territories and control important harbours like Castletownbere. Castle Dhermod would have been strategically positioned to oversee maritime traffic and protect the approaches to the harbour, which has been a crucial anchorage since medieval times. The castle’s builder, Dhermod McCarthy, was likely connected to the broader network of McCarthy strongholds that dotted the Cork coastline, each serving as both defensive fortifications and symbols of Gaelic authority.

While no visible traces remain above ground today, the site at Foildarrig continues to hold archaeological significance. The complete absence of surface remains suggests the stone may have been robbed for building materials over the centuries, a common fate for abandoned castles in Ireland. The location itself, recorded in historical documents and early maps, preserves the memory of this once formidable structure that played its part in the complex tapestry of Gaelic and Anglo-Norman power struggles that shaped medieval Cork.