(French) form of Diana, now also widely used in the English-speaking world. It was especially popular among the Renaissance aristocracy, who loved hunting and were therefore proud to name their daughters after the classical goddess of the chase.
English: habitational name from an unidentified place. There is a place so named on the Isle of Wight (and one called Swainstone in Devon). However, in England the surname is concentrated in County Durham, suggesting that it could be a variant of the habitational name Swanston.