Abridged from Harpokration s.v., who cites Aeschines (3.171, for the phrase "Nymphaion on the Black Sea") as well as Krateros. The qualifier was necessary to differentiate it ["Place of the Nymphs"] from its many homonyms; cf. gamma 478.
See also -- for quite different information -- Stephanus of Byzantium s.v., citing Strabo.
[1] Krateros FGrH 342 F8. The allusion is to the C5 BC Athenian Empire, of which Nymphaion was a tribute-paying member. See in brief Russell Meiggs, The Athenian Empire (Oxford 1972) 329.
See Princeton Encyclopedia of Classical Sites entry at web address 1.