Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† ervum (her-), i, n. [Gr. ἐρέβινθος, ὄροβος; root, ar- for al-; cf. alo], a kind of pulse, the bitter vetch, ervum ervilia, Linn.; Verg. E. 3, 100 Voss.; Col. 2, 10, 34; 11, 2, 10; Pall. Jan. 8; Ov. Med. fac. 55; Hor. S. 2, 6, 117.