Description of Sinclair:

Derived from a Norman French town called "Saint Clair". "Clair" is ultimately derived from "Clarus," which meant "clear, bright, famous". The name Clarus was borne by a few early saints. The feminine form was popularized by the 13th-century Saint Clare of Assisi (called Chiara in Italian), a friend and follower of Saint Francis, who left her wealthy family to found the order of nuns known as the Poor Clares.