Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Firmĭus, ii, m.,a Roman proper name, e. g. FirmiusCatus, Tac. A. 2, 27;4, 31. Hence, Firmĭānus, a, um, adj.,of Firmius, an unknown silver-worker of that name: Firmiana vasa, Plin. 33, 11, 49, § 139 (Jan. Furniana).