Meaning

noun an embankment built around a space for defensive purposes

noun a fencelike structure around a deck (usually plural)

noun a protective structure of stone or concrete; extends from shore into the water to prevent a beach from washing away

originFrom Middle English bulwerk, from Middle Dutch bolwerk, bolwerc and Middle Low German bolwerk, equivalent to bole (“tree trunk”) + work. Cognate with German Bollwerk, Danish bolværk, Swedish bålverk, Dutch bolwerk. Doublet of boulevard (from French boulevard, from Dutch); cognate with Portuguese and Spanish baluarte and Italian baluardo.

Etymology from Wiktionary, CC BY-SA 3.0