[French, perhaps (via West Indian Creole tafiat, formula used to toast a person's health) from New Latin *rata fiat (rēs or conventiō), let (the thing or the agreement) be confirmed (from the practice of concluding a contract with a drink ) : Latin rata, feminine of ratus, past participle of rērī, to reckon, settle; see RATE¹ + Latin fiat, let it be done, third person singular present subjunctive of fierī, to become, be done; see FIAT.]