etui (n.)youdaoicibaDictYouDict[etui 词源字典]
1610s, also ettuy, etwee from French étui, Old French estui (12c.) "case, box, container," back-formation from estuier "put in put aside, spare; to keep, shut up, imprison," which is of uncertain origin. Perhaps from Latin studere "to be diligent."[etui etymology, etui origin, 英语词源]