c. 1300, "order or direct with authority" (transitive), from Old French comander "to order, enjoin, entrust" (12c., Modern French commander), from Vulgar Latin *commandare, from Latin commendare "to recommend, entrust to" (see commend); altered by influence of Latin mandare "to commit, entrust" (see mandate (n.)). In this sense Old English had bebeodan.
Intransitive sense "act as or have authority of a commander, have or exercise supreme power" is from late 14c. Also from late 14c. as "have within the range of one's influence" (of resources, etc.), hence, via a military sense, "have a view of, overlook" in reference to elevated places (1690s). Related: Commanded; commanding.
Command-post "headquarters of a military unit" is from 1918. A command performance (1863) is one given by royal command.