mid-14c., "one to whom special duty is entrusted by a higher power," from Medieval Latin commissarius, from Latin commissus "entrusted," past participle of committere (see commit). Originally ecclesiastical; the military sense of "official in charge of supply of food, stores, transport" dates to late 15c. Hence "storeroom" (1882) and "dining room in a larger facility" (1929, American English).