Two names: Coney Island, of disputed origin, and the settler Nicholas Stillwell.
Stillwell Avenue is named after Nicholas Stillwell (1603–1671), who had a farm in the area and founded an influential Brooklyn family. ‘Coney’ is an old word for rabbit, and the most popular theory links the name to Dutch ‘konijn’; early-17th-century Dutch maps show ‘Conyne Eylandt’. In 1816 Egbert Benson argued for ‘Conyn’s Island’, after a Dutch surname. There is no clear consensus.