Lewis & Short

Sūnĭum or Sūnĭon, ii, n., = Σούνιον, a promontory and town of Attica, now Capo Colonna, Mel. 2, 2, 8; 2, 3, 6; Cic. Att. 13, 10, 3; 7, 3, 10; Plin. 4, 7, 11, § 24; Ter. Phorm. 5, 5, 9; id. Eun. 3, 3, 13; Liv. 28, 8; 31, 22; 32, 17.
Form Sunion, Ov. F. 4, 563; Stat. Th. 12, 625.