Donner sa langue au chat
[duh nay sa la(n) go sha
To give up, stop guessing
To give one's tongue to the cat
The French expression donner sa langue au chat
is used to indicate that you don't know the answer - you can't think of anything else and have no idea what it is that another person is trying to make you guess.
I don't know why you would give your tongue to the cat at this point - is she supposed to continue guessing for you? And is there any connection to the English expression "cat got your tongue?" (The French equivalent of that, by the way, is Tu as avalé/perdu ta langue ?
- Tu ne devineras jamais qui va venir nous voir !
- Paul ?
- Non !
- David ?
- Non !
- Alors, je donne ma langue au chat.
- You'll never guess who's coming to visit!
- OK, I give up.