Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† tĕtănus, i, m., = τέτανος, a stiffness or spasm of the neck, tetanus, Plin. 23, 1, 24, § 48; 31, 10, 46, § 122; Scrib. Comp. 101 (in Cels. 4, 3, written as Greek).