Lewis & Short

Āpennīnus (better Appennīnus, Verg. A. 12, 703 Cod. Med.; also APENINVS, Inscr. Grut. 204, 18), i, m. [from the Celtic penn, mountain-summit], the mountainchain that passes through the length of Italy, the Apennines, Plin. 3, 5, 7, § 48; conspicuous for height; hence, celsus Appenninus, Hor. Epod. 16, 29: Appenninus nubifer, Ov. M. 2, 226.
Personified: gaudetque nivali Vertice se attollens pater Appenninus ad auras, Verg. A. 12, 703; cf. Mann. Ital. 1, 264 sq.