An Etymological Dictionary of the German Language/Käfig
Käfig, m. and n., ‘cage, gaol,’ from MidHG. kęvje, m., f., and n., ‘cage (for wild animals and birds),’ also ‘prison’; the j of the MidHG. word became g (comp. Ferge and Scherge). OHG. chęvia, f., is derived from Low Lat. cávia, Lat. cặvea, ‘birdcage’ (respecting HG. f for Lat. v, comp. Pferd, Vers, and Verdikt), whence also ModHG. Kaue. Allied to the Rom. words, Ital. gabbia, gaggia, Fr. cage (hence E. cage), and Ital. gabbiuolo, Fr. geôle (E. jail, gaol), ‘prison.’ Further, Bauer first obtained the meaning ‘cage’ in MidHG.