Some ‘handy’ idioms – croiser les doigts, for example – translate easily. Fingers crossed, anyway.
Others are so close to their English equivalent that any guesses do not have to be educated. It is not hard to work out that anyone with la main verte (a green hand) will have a beautiful garden. And it is no great leap from knowing a place like the back of your hand to knowing it sur le bout des doigts (on the end of your fingers).
But French can trip you up with a few bodily differences, and you would not want to put your foot in it – especially as the French for putting your foot in it is the painful se mettre le doigt dans l’oeil (literally, and indeed figuratively, to put your finger in your eye). If you did, you’d regret it and French has a handy and agonising idiom for that too, s’en mordre les doigts (to bite your fingers).
Fingers and eyes are also linked in an idiom for avoiding putting your foot in it by following rules to the letter – or au doigt et à l’oeil (by the finger and the eye).
The French for ‘nimble-fingered’ is the beautiful des doigts de fée (fairy fingers). On the other hand, the more disgusting les doigts dans le nez (fingers in the nose) describes a task that is straightforward. English would have us do the same task ‘standing on our heads’.
If you offer a helping hand, you stick la main à la pâte (put a hand in the pastry), while mettre le doigt dans un engrenage means putting your finger, rather than that body part favoured by the Anglo Saxons, in gear.
If you don’t want to reveal the identity of someone who told you a secret, you may say mon petit doigt me l’a dit, the French equivalent of ‘a little bird told me’. If you do let their identity slip, someone may faire un doigt d’honneur (show you the honour, or middle, finger). And you really do not want that.