From the name of a town in southern France, possibly derived from Occitan mair “mother” and French lys “lily”. It is also sometimes considered a combination of Marie and lys.
From the Old English elements os “god” and mund “protection”. During the Anglo-Saxon period a Norse cognate Ásmundr was also used in England, and another version was imported by the Normans. Saint Osmund was an 11th-century Norman nobleman who became an English bishop. Though it eventually became rare, it was revived in the 19th century, in part from a surname that was derived from the given name.