What is "gairsay"

Gairsay ( Old Norse: Gáreksey) is a small island in Orkney, Scotland, located in the parish of Rendall, off the coast, astride one of the approaches to the bays of Firth and Kirkwall. It is about long and wide and includes one conical hill and a small harbour called Millburn Bay, which is sheltered by the peninsula known as the Hen of Gairsay.