c. 1600, "to be in effect, perform or be at work, exert force or influence," a back-formation from operation (q.v.), or else from Latin operatus, past participle of operari "to work, labor, toil, take pains" (in Late Latin "to have effect, be active, cause"). The surgical sense of "perform some manual act upon the body of a patient," usually with instruments, is attested from 1799. Meaning "to work machinery" is from 1864 in American English. Related: Operated; operating. Operating system in the computer sense is from 1961.