operative (adj.)youdaoicibaDictYouDict[operative 词源字典]
"producing the intended effect," early 15c., from Old French operatif (14c.) or directly from Late Latin operativus "creative, formative," from operat-, past participle stem of operari (see operation). Weakened sense of "significant, important" is from 1955.[operative etymology, operative origin, 英语词源]
operative (n.)youdaoicibaDictYouDict
"worker, operator," 1809, from operative (adj.); sense of "secret agent, spy" is first attested 1930, probably from its use by the Pinkerton Detective Agency as a title for their private detectives (1905).