Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Eterëĭus, i, m., a freedman of the Roman knight Corellius, Plin. 17, 17, 26, § 122.
Hence, Eterëĭānus, a, um, adj., of Etereius: nux, Plin. 15, 23, 25, § 94; 17, 17, 26, § 122.