Boulevard
mid 18th century: French, ‘a rampart’ (later ‘a promenade on the site of one’), from German Bollwerk (see bulwark).
wiktionary
Borrowed from French boulevard, from Middle French boulevard, bollevart, boulevars, bolevers, bollewerc(“promenade, avenue, rampart”), from Middle High German bolewerc, bolwerc (modern German Bollwerk) or Middle Dutch bolwerk(“ bulwark, bastion”). Doublet of bulwark; more at bole, work.
etymonline
boulevard (n.)
1769, "broad street or promenade planted with rows of trees," from French boulevard, originally "top surface of a military rampart" (15c.), from a garbled attempt to adopt Middle Dutch bolwerc "wall of a fortification" (see bulwark) into French, which at that time lacked a -w- in its alphabet.
The notion is of a promenade laid out atop demolished city walls, a way which would be much wider than urban streets. Originally in English with conscious echoes of Paris; in U.S., since 1929, used of multi-lane limited-access urban highways. Early French attempts to digest the Dutch word also include boloart, boulever, boloirque, bollvercq.
