Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ē-dĕcĭmo (-decumo), no perf., ātum, 1, v. a. (to select the tithes; hence, in gen.), to pick out, select (late Lat.), Symm. Ep. 5, 81; 9, 21; Macr. S. 1, 5; 2, 1; cf.: edecimata (ex-) electa, Paul. ex Fest. p. 80, 6 Müll.