Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
com-mercor (con-m-), ātus, 1, v. dep., to trade, traffic together, buy up, purchase (except in Sall., only ante-class.): captivos, Plaut. Capt. prol. 26; 1, 1, 32: cives, homines liberos, id. Pers. 4, 9, 12: arma, tela, etc., Sall. J. 66, 1.
Hence, commercātus, a, um, Part. in pass. signif.: edulia, Afran. ap. Non. p. 28, 30.