Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
gerres, is, m., an inferior salted seafish, Plin. 32, 11, 53, § 148 Sill. (al. girres), Mart. 12, 32, 15; 3, 77, 7; cf.: gerres μαινίδες, Gloss. Philox.
Prov.: addere garo gerrem, i. e. to add to what is precious something worthless, Arn. 5, 188.