Lewis Short
Narnĭa | Narnĭensis, ĭum | Narnĭenses (noun F.m) : ae.
* An Umbrian city on the Nar, now Narni, Liv. 10, 10; 27, 9; 29, 15; Tac. A. 3, 9.—Hence
* Adj., of or belonging to Narnia, Narnian: ager,Plin. 31, 4, 28, § 51: equites,Liv. 27, 50.—As subst.: (sc. ager),Plin. Ep. 1, 4, 1.— In plur. subst.: , , , the inhabitants of Narnia, the Narnians, Plin. 3, 14, 19, § 113.
Charlton T. Lewis, Charles Short, A Latin Dictionary