An Etymological Dictionary of the German Language/Kapaun
Kapaun, m., ‘capon,’ from the equiv. MidHG. kappûn; borrowed after the era of the substitution of consonants from Rom. cappônem (Lat. capo, equiv. to Gr. κἀπων); comp. Ital. cappone, Fr. chapon (whence also Serv. kopun). Even in the AS. period capûn, ‘gallinaceus,’ is found derived from the same source (E. capon); comp. Du. kapoen. From the Lat. nom. cappo is derived MidHG. kappe, and even OHG. chappo. For another term see under Hahnrei.