Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
mercĭmōnĭum, ii, n. [merx], goods, wares, merchandise (ante-class. and postAug.): in vostris mercimoniis Emundis vendundisque, Plaut. Am. prol. 1; id. Most. 3, 3, 9; 12: quid agit meum mercimonium apud te? id. Curc. 4, 4, 8: videre cupio nostrum mercimonium, Turp. ap. Non. 213, 8: per tabernas, quibus id mercimonium inerat, quo flamma alitur, Tac. A. 15, 38.