Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sannĭo, ōnis, m. [sanna], one who makes mimicking grimaces, a buffoon (cf. scurra), Cic. de Or. 2, 61, 251; id. Fam. 9, 16, 10; Amm. 14, 6, 16.