Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Tarbelli, ōrum, m., a people in Aquitanian Gaul, extending southwards from Burdigala to the Pyrenees, in the neighborhood of the mod. Dax, Caes. B. G. 3, 27; Plin. 4, 19, 33, § 108; 31, 2, 2, § 4.
Hence,