achæmenian

from The Century Dictionary.

• Pertaining or relating to the Achæmenidæ, an ancient royal family of Persia, historically beginning with Cyrus, about 558 b. c., and ending with the conquest of the Persian empire by Alexander the Great, 330 b. c.
• noun A Persian of the time of Achæmenes or the Achæmenidæ; also, the Persian language of that period (recorded in cuneiform inscriptions).