take a French leave

Verb

take French leave (third-person singular simple present takes French leave, present participle taking French leave, simple past took French leave, past participle taken French leave)

1. (dated, idiomatic, informal, intransitive) To leave quietly and unnoticed, without asking for permission or informing anyone; to slip out.
   • As for Ditton, after all his courting, and his compliment, he ſtole avvay an Iriſhman's bride, and took a French leave of me and his maſter; […]1771, [Tobias Smollett], “To Mrs. Mary Jones, at Brambleton-hall”, in The Expedition of Humphry Clinker […], volume II, London: […] W. Johnston, […]; and B. Collins, […], →OCLC, page 226

   Synonyms:

   duck out, sneak out

2. (dated, euphemistic, idiomatic, informal, intransitive, specifically) To desert or be temporarily absent from duty or service without permission; to go absent without leave (AWOL).
   • That officer […] reminded Burton of the necessity there was that all the officers of the Spitfire should hold themselves in readiness, as a court-martial was sure to be ordered relative to the loss of that ship: that order might possibly be telegraphed down, and he must therefore decline granting...1829, [William Nugent Glascock], “The Return”, in Sailors and Saints; or, Matrimonial Manœuvres. […], volume II, London: Henry Colburn, […], →OCLC, pages 222–223