Originally a male pet form of James and still so used, especially in Scotland and Northumberland. It is now also found as a girl's name, a feminine equivalent of James, especially in North America, where it is used more frequently for girls than boys. It is famously borne by the actress Jamie Lee Curtis (b. 1958), and is often used in combination with Lee or its variants.
English (southern): patronymic either from the personal name Simon (see Simon) or, as Reaney and Wilson suggest, from the medieval personal name Simund (composed of Old Norse sig ‘victory’ + mundr ‘protection’), which after the Norman Conquest was taken as an equivalent Simon, with the result that the two names became confused.