Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
2. Lĭbo, ōnis, m., a Roman surname in the gens Marcia and Scribonia, Cic. Att. 12, 5, 3; id. Brut. 23, 89; id. de Or. 2, 65, 263; id. Ac. 1, 1, 3; Hor. Ep. 1, 19, 8.