[16C proper name Barbary Coast, the countries of the northern coast of Africa; as a sl. term the phr. has applied spec. to the San Francisco waterfront before the 1906 earthquake, Water Street, New York City, and part of Elizabeth Street, Sydney (from Campbell Street to Devonshire Street) during WWII; also Monkwearmouth area of Sunderland DSUE cites late 17C–early 19C Little Barbary, Wapping, home of the Ratcliff Highway, once London’s tough port area]
[mid-19C–1940s] the ‘red-light’ area of a city, esp. as frequented by sailors on leave.