verb/mɛ.tʁə sa mɛ̃ a ku.pe/
to bet one's life that, to bet one's boots that, to bet one's bottom dollar that (to be absolutely sure that)
“J'en mettrais ma main à couper.”
Synonyms: donner sa main à couper, mettre sa main au feu, mettre sa tête à couper
Compare Polish dać sobie rękę uciąć.