Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. brĭgantes, um, m., a species of small worm in the eyelashes, Marc. Emp. 8.
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.