An Etymological Dictionary of the German Language/Annotated/Bollwerk

by Friedrich Kluge

Bollwerk, neuter, ‘bulwark, bastion,’ from late Middle High German bolwerk, ‘catapult, bulwark,’ in the former sense cognate with the preceding word; in the latter probably connected with Bohle; Dutch bolwerk, English bulwark. The Teutonic word in the sense of ‘bulwark,’ which belongs to it since the 15th century, found its way into Slavonic and Romance (Russian bolverk, French boulevard).