Lewis Short
Nīgris | Nīgir, ārum | Nī-ger | Nīgrītae (noun M.m) : (, Vitr. 8, 2, 6; , Mart. Cap. 6, § 673)
* A river in the interior of Africa, now the Joliba or Niger, Plin. 5, 4, 4, § 30; 8, 21, 32, § 77.— Hence, , , , the people living near the Niger, Mel. 1, 4, 3; 3, 10, 4; Plin. 5, 8, 8, § 43.
Charlton T. Lewis, Charles Short, A Latin Dictionary