Premise: Kisimul Castle (Scottish Gaelic: "Caisteal Chiosmuil" ) and also known as Kiessimul Castle, is a small medieval castle located on a small island off Castlebay, Barra, in the Outer Hebrides, Scotland. It gets its name from the Gaelic "cìosamul" meaning "castle island".
Hypothesis: Caisteal Chiosmuil means castle island.