1769, from Fr., originally "top surface of a military rampart," from a garbled attempt to adopt M.Du.
bolwerc "wall of a fortification" (see
bulwark) into Fr., which lacks a
-w-. The original notion is of a promenade laid out atop demolished city walls, which would be much wider than urban streets. Originally in Eng. with conscious echoes of Paris; since 1929, in U.S., used of multi-lane limited-access urban highways.