King's Island sits in a bay better known for its role in the dramatic French expedition of 1798, when General Humbert landed at Killala with around a thousand troops in a short-lived attempt to support the United Irishmen's rebellion. That episode left its mark on almost every feature of this coastline, and the island's name may well belong to the same contested, layered history that makes the bay itself so difficult to read at a glance.

Beyond the name and its setting, the documentary record for the island is thin enough that firm conclusions are difficult to draw. Killala Bay has been inhabited and navigated since prehistoric times, and islands of this kind along the Irish northwest coast frequently served as refuges, fishing stations, or sites of early ecclesiastical settlement. The bay takes its name from the town of Killala, whose round tower and early Christian associations suggest a community of considerable antiquity. Whether the island figures in any of that longer history remains, for now, an open question.