An Etymological Dictionary of the German Language/Annotated/Quitte
Quitte, feminine, ‘quince,’ from the equivalent Middle High German quiten, feminine (Old High German *quitina is wanting), with the remarkable variant küten, from Old High German chutina (Swiss χütene), ‘quince.’ This latter form alone renders it possible that Quitte was borrowed from the equivalent Romance cotônea, which is probably represented by Italian cotogna and French coing (whence English quince and Dutch kwee). The connection between Latin cotônea (parallel form cottanum) and Greek κυδώνεα is obscure, and so is the relation of Old High German *quitina to chutina. if the word was borrowed, it was introduced contemporaneously with Pflaume.