Originally, the custom (in the 18th c. prevalent in France and sometimes imitated in England) of going away from a reception, etc., without taking leave of the host or hostess. Hence, jocularly, to take French leave is to go away, or do anything, without permission or notice.
1771. Smollett, Humph. Clinker (1895), 238. He stole away an Irishman’s bride, and took a French leave of me and his master.
1772. Town & Country Mag., IV. Jan., 33. She accepted of the proposal, and left Fanny with French leave, and all her cloaths, except those upon her back.
1775. J. Jekyll, Corr. (1894), 28. They [French etiquettes] are precise to a degree. For example, I will allow that the single circumstance of taking French leave (which gains ground even among us at present) is easy and natural. But, on the contrary, I will maintain that there is more formality of compliment in entering one assembly here [France] than in taking the round of routs for a whole winter in London.
1775. Trusler, Chesterfield’s Princ. Politeness (ed. 4), 72. As the taking what is called a French leave was introduced that on one person’s leaving the company the rest might not be disturbed, looking at your watch does what that piece of politeness was designed to prevent.
1821. W. Gifford, in Smiles, J. Murray (1891), II. xxi. 55. The few teeth I have seem taking their leave—I wish they would take a French one; and after so long an acquaintance they do not like to part without pain.
1866. Mrs. H. Wood, St. Martin’s Eve, xiii. Her roving son had taken French leave to go back to London.
