More precisely, a city of that name, for which this entry gives 2 alternative ethnics. Stephanus of Byzantium s.v. Kydonia (Ethnica 390-391) gives more still: Kydon, Kydonios, Kydonaios, Kydonikos.
Stephanus headlines Kydonia as 'a city of Crete' (presumably the one meant here), and adds that there was a second in Sicily and a third in Libya.
The Cretan Kydonia was on the western end of the island; see Barrington Atlas map 60 grid B1. The Sicilian city is unlocated but perhaps near Lipara. The Libyan city's location is completely unknown. There was perhaps another one on the island of Kos.