Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Ăchīvus, a, um (gen. plur. Achivom, Verg. A. 11, 266), adj. [fr. Achaeus, with the Digamma, Achaefos, Achifus, Achivus], Achaean, Grecian (v. Achaia): tellus, Ov. Pont. 1, 4, 33: castra, id. H. 1, 21.
Hence, Ăchīvi, the Greeks, Cic. Div. 1, 14: quidquid delirant reges plectuntur Achivi, whatever wrongs the (Grecian) kings are guilty of (before Troy) their subjects must suffer for; but it soon became a general proverb: whatever errors the great commit, the people must atone for, Hor. Ep. 1, 2, 14.