late 14c., "impetuous, unrestrained," from Old French furios, furieus "furious, enraged, livid" (14c., Modern French furieux), from Latin furiosus "full of rage, mad," from furia "rage, passion, fury" (see fury). Furioso, from the Italian form of the word, was used in English 17c.-18c. for "an enraged person," probably from Ariosto's "Orlando Furioso."