Also 6–7 catchet. [Fr.; f. cacher to conceal: in 18th c. treated as English.]
1. A seal. Letter of cachet (F. lettre de cachet): a letter under the private seal of the French king, containing an order, often of exile or imprisonment.
a. 1639. Spottiswood, Hist. Ch. Scotl., IV. (1677), 193. She had appointed, in stead of his hand, a Cachet to be used in the signing of Letters.
1754. Erskine, Princ. Sc. Law (1809), 177. On the accession of James VI. to the crown of England, a catchet or seal was made, having the King’s name engraved on it, with which all signatures were to be afterwards sealed.
1753. Scots Mag., XV. 62/2. He obtained a letter of cachet.
2. fig. Stamp, distinguishing mark, ‘sign manual.’
1840. Thackeray, Paris Sk. Bk. (1885), 69. All his works [pictures] have a grand cachet: he never did anything mean.
1882. Pebody, Eng. Journalism, xxii. 176. The journal in which the cachet of fashionable life is to be distinguished.
3. attrib. Done under letter of cachet; privy, secret.
1837. Fraser’s Mag., XVI. 293. Abominators of all close, cachet, muffled … proceedings.
