Word Origin and History for wash one's dirty linen in public
"cloth from woven flax," early 14c.; earlier as an adjective, "made of flax" (c.1200), from Old English linin (adj.) "made of flax," from lin "flax, linen thread, cloth," from West Germanic *linam (cf. Old Saxon, Old Norse, Old High German lin "flax, linen," German Leinen "linen," Gothic lein "linen cloth"), probably an early borrowing from Latin linum "flax, linen," which, along with Greek linon is from a non-IE language.
Idioms and Phrases with wash one's dirty linen in public
wash one's dirty linen in public
Also air one's dirty linen or laundry. Expose private matters to public view, especially unsavory secrets. These metaphors are reworkings of a French proverb, Il faut laver son linge sale en famille (“One should wash one's dirty linen at home”), which was quoted by Napoleon on his return from Elba (1815). It was first recorded in English in 1867.