Belgæ, The people that inhabite the countries and Townes inclosed with the Oeean Sea, and the riuers of Rhene, Marne, and Seyne, wherein be the Cities of Tryre, Coleyne, Magunce, and Reynes. Also the Countries of Flaimders, Hollande, Gelder, Iuliers, Cleues, Hennawe, parts of Friselande, Picardie, the greatest part of Campaine, and all the Forrest of Ardeme. It was sometime calted Gallia Belgica.
Lewis and Short: Latin dictionary
Belgae, ārum, m., = *be/lgai [Balge, in Lower Germany, a low, swampy region], the Belgians, a warlike people, of German and Celtic origin, in the north of Gaul, Caes. B. G. 1, 1; 2, 4; Mel. 3, 2, 4; Tac. A. 1, 43; 3, 40; id. H. 4, 17; 4, 76 al.—In sing.: Bel-ga, ae, m., a Belgian, Luc. 1, 426; Claud. Laud. Stil. 1, 226.—II. Deriv.: Belgĭ-cus, a, um, adj., Belgic: esseda, Verg. G. 3, 204: color, Prop. 2 (3), 18, 26: calami, Plin. 16, 36, 65, 161: canis, Sil. 10, 80.—Hence, Gallia Belgica, or absol. Belgica, the northern part of Gaul, between the Rhine, Seine, Marne, and the North Sea, inhabited by the Belgians, Plin. 4, 17, 31, 105; 7, 16, 17, 76. —Absol., Plin. 15, 25, 30, 103; Tac. H. 1, 12; 1, 58 al.