Lewis & Short

Bătāvus, a, um, adj., pertaining to Batavia, Batavian, of Holland, Dutch: spuma, Mart. 8, 33, 20.
Hence, Batāvi, ōrum, m., = Βατάουοι, Ptol., the Batavians, Hollanders, Dutch, Tac. H. 4, 12; id. G. 29 al.: Batavorum Insula, v. Batavia.
With penult scanned short: Vangiones Bătăvīque truces, etc., Luc. 1, 431.
Sing.: Bătā-vus, i, m., one of the Batavi, Mart. 14, 176.
Collectively, Juv. 8, 51; Sil. 3, 608.