Literal translation
to break into a great sweat, the three sweats
Meaning
to be scared stiff
Explanation
To be very afraid. The Provençal verb tressusa means to sweat profusely, built from susa, to sweat, and the intensifying prefix tres-. As that prefix became rare and unrecognizable, the word tressusour came to be heard as tres susour, three sweats, giving rise to the French phrase avoir les trois sueurs. A rarer, even more emphatic variant exists too, avoir les quatre sueurs.