Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† mĕtōnymĭa, ae, f., = μετωνυμία, a figure by which one name is changed for another, a change of names, metonymy (pure Lat. denominatio), Paul. ex Fest. p. 153 Müll.; Charis. p. 244 P. al.