Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
3. Ancōn, ōnis, or Ancōna, ae, f. [v. ango], = Ἀγκών, an ancient seaport town in the north of Picenum, situated on a promontory forming a remarkable curve or elbow, as the name implies, founded by the Syracusans, still called Ancona; form Ancōna, Cic. Phil. 12, 9, 23; id. Fam. 16, 12, 2; Caes. B. C. 1, 11; Plin. 2, 72, 74, § 182; 3, 13, 18, § 111 sq. al.
Form Ancōn, Mel. 2, 4, 5; Cat. 36, 13; Sil. 8, 438; Juv. 4, 40 al.; and in a pun: Cingulum nos tenemus; Anconem amisimus, Cic. Att. 7, 11, 1.