Avoir un poil dans la main

Literally: To have a hair in the hand

Example: “Mon colocataire ne fait jamais la vaisselle, il a un poil dans la main.” — My roommate never does the dishes; he's bone idle.

English equivalent: To be bone idle

Origin: First recorded with its modern sense in 1808, in Charles-Louis d'Hautel's dictionary of low-register French, defined there as being disposed to do nothing at all. Nobody has ever settled why the hair is there, though the guesses agree on the logic even without a documented source: hands that are never used, and so never rubbed or worn by any friction, are free to grow one where a busy hand never could. A cheekier variant imagines the hair as something precious you were trusted to hold, giving you the perfect excuse — a closed fist — for refusing every task afterward.