Leather boiled in water, then moulded into shape, which, when dry, hardened sufficiently to be carved for use as cheap armour. In 1278, Edward I held a *behourd in which all the armour was cuir-bouilli. The only distinctions were that the noblest jousters were permitted golden *helms, while the lesser wore silver. [< OldFr. cuir = leather + bouillir = boil] -
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.