Origin of the name Sydney:

Transferred use of the surname originating as a Norman baronial name taken from the place-name St. Denis in Normandy. Alternatively, the name arose independently in England and is derived from the Old English elements sīd (extensive, wide) and ieg (island in a river, riverside meadow). The name was indicative of one who dwelled on or near the wide, riverside meadow, or from the wide island.

From A World of Baby Names by Teresa Norman.Buy the book