An Etymological Dictionary of the German Language/Annotated/Küchlein
Küchlein, neuter, ‘chicken,’ Modern High German only; a Middle German and Low German word introduced by Luther into High German (in Upper German dialectic hüenli, West Middle German hünkel, Suabian luggele). To the Middle German and Low German küchen, küken, correspond Anglo-Saxon čŷčen (plural čŷcnu), Middle English chîken, English chick, chicken, Scandinavian kjúklingr, Dutch kieken, keuken. The Gothic diminutive termination -îna- (*kiukein) frequently occurs in the names of animals, Gothic gait-ein, Anglo-Saxon tiččen (Gothic *tikkein), Anglo-Saxon hêčen (Gothic *hôkein), neuter ‘kid’; see Füllen, Geiß, Schwein, Zicklein, and Mädchen. The substantive on which the word is based is Anglo-Saxon cocc, English cock, Scandinavian kokkr (to which Gothic *kiukein, neuter, is related by gradation). There is no reason for thinking that the Teutonic word was borrowed from Romance — French coq, like Anglo-Saxon cocc (Upper German gockel, gückel), is a recent onomatopoetic term also, for Welsh and Cornish cog, ‘cuckoo,’ points also to the base cucâ (so too Old Irish cúach, ‘cuckoo,’ from coucâ). Compare Kuckuck.