Lewis & Short

2. Brĭgantes, um (acc. Brigantas, Tac. A. 12, 32), m., the most northern and powerful people in Roman Britain, subdued by Cerialis, Tac. A. 12, 32; id. H. 3, 45; id. Agr. 17; Juv. 14, 196.
Hence, Julius Briganticus, a son of the sister of Civilis, Tac. H. 4, 70; 2, 22; 5, 21.