cachetyoudaoicibaDictYouDict[cachet 词源字典]
cachet: [17] Cachet was a Scottish borrowing of a French word which originally meant ‘seal affixed to a letter or document’. In the 19th century this developed into the figurative ‘personal stamp, distinguishing characteristic’, which, through its use in the context of distinguished or fashionable people or things, has come to mean ‘prestige’. The original notion contained in the word is of ‘pressing’.

It comes via the medieval French verb cacher ‘press’ from Latin coactāre ‘constrain’. This was a derivative of coact-, the past participial stem of cōgere ‘drive together’ (source of English cogent), a compound verb formed from con- ‘together’ and agere ‘drive’ (source of English act and a host of other derivatives from agent to prodigal).

Modern French cacher means ‘hide’, which is the source of cache ‘hoard’, borrowed by English in the 19th century.
=> cache, cogent[cachet etymology, cachet origin, 英语词源]
cachet (n.)youdaoicibaDictYouDict
1630s, Scottish borrowing of French cachet "seal affixed to a letter or document" (16c.), from Old French dialectal cacher "to press, crowd," from Latin coactare "constrain" (see cache). Meaning evolving through "(letter under) personal stamp (of the king)" to "prestige." Compare French lettre de cachet "letter under seal of the king."