Tirer les vers du nez

Literally: To pull worms from the nose

Example: “Elle ne voulait rien dire, mais j'ai fini par lui tirer les vers du nez.” — She didn't want to say anything, but I finally got it out of her.

English equivalent: To worm something out of someone

Origin: Attested since the 15th century, and admitted by every serious source to be genuinely unexplained — Alain Rey calls the leading theories unconvincing and says so in print. One candidate derives it from Latin verum, the truth, deformed into vers (worms) along the way, so the nose would originally have yielded truth rather than parasites — Rey rejects this partly because the English equivalent, to worm a secret out of somebody, keeps the worm image intact rather than pointing at any buried truth. A second theory reaches for the quacks of an earlier age who claimed to cure the sick by drawing worms out through the nose, worms being blamed for whatever illness was in question. A near-identical Latin tag, exuere verum cujusdam nasu, shows the image is old regardless of which story explains it.