An Etymological Dictionary of the German Language/Zwinger

by Friedrich Kluge

Zwinger, m., ‘fortified castle, prison, narrow space, wild beast’s cage, arena,’ from MidHG. twingœre, m., ‘oppressor, space between the walls and ditch of a citadel, promurale, fortress.’ Comp. Dan. twinger, ‘prison, wild beast's cage’ (Du. dwinger, ‘despot, tyrant’).