Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Ăchaemĕnēs, is, m., = Ἀχαιμένης, the ancestor of the old Persian kings, grandfather of Cyrus: dives Achaemenes, poet. for great or Asiatic wealth in gen., Hor. C. 2, 12, 21.