Comments:A Tung.-Jpn. isogloss. It is worth noting Yak. kuba 'swan' - usually derived from PT *Kugu, but with a quite inexplicable -b-; it is, in fact, possible that some other Turkic forms - cf. Turkm. Guv, Nogh. quv etc. also go back to PT *Kub(a) - naturally confused in most modern languages with the reflexed of *Kugu (see under *kū̀gù).