An Etymological Dictionary of the German Language/Bollwerk

by Friedrich Kluge

Bollwerk, n., ‘bulwark, bastion,’ from late MidHG. bolwerk, ‘catapult, bulwark,’ in the former sense cognate with the preceding word; in the latter probably connected with Bohle; Du. bolwerk, E. bulwark. The Teut. word in the sense of ‘bulwark,’ which belongs to it since the 15th cent., found its way into Slav. and Rom. (Russ. bolverk, Fr. boulevard).