commander (n.)

"one who has the authority or power to command or order," early 14c., comandur, from Old French comandeor "commander, commandant," from comander "to order, enjoin" (see command (v.)). Commander in chief "commander of all the armies of a state" is attested from 1650s. In the U.S., by the Constitution, it is the president; George Washington was so called by 1778.