The reality is rather different. The structure is a 19th-century house, built by a member of the O'Donnell family, which borrowed its name from a genuine medieval castle located roughly 1.1 kilometres to the north-west.

The borrowed name is the curious detail here. Trough Castle, the actual castle, survives as a separate ruin a short distance away, and it was that older fortification which lent its identity to the later house. Whether by local habit or deliberate association, the O'Donnell family's 19th-century building absorbed the castle's name so thoroughly that the Ordnance Survey cartographers recorded it under that title, parenthetical ruin status and all, as if the house itself were the ancient thing. It is a small but telling example of how names migrate across a landscape, attaching themselves to new structures and occasionally misleading those who read maps too literally.