Taken from the same entry in Photius' Lexicon (kappa705 Theodoridis), though with a change of accentuation.
See LSJ s.v. ki/qaros: s.v. I: "chest" (in Hippocrates), s.v. II "flatfish". The variant accentuation also appears in Strabo 17.2.4, referring to the fish.
The Etymologicum Gudianum and the Etymologicum Magnum attempt to derive the meaning "chest" from the kithara (kappa 1590), "because of the similarity of the bones to the strings". The word is also glossed by Erotian ("a name for the chest in Doric") and Hesychius kappa2634 ("breast, rib; also a fish").