"estimated value or worth," early 15c., from Old French rate "price, value" and directly from Medieval Latin rata (pars) "fixed (amount)," from Latin rata "fixed, settled," fem. past participle of reri "to reckon, think" (see reason (n.)). Meaning "degree of speed" (prop. ratio between distance and time) is attested from 1650s. Currency exchange sense first recorded 1727. First-rate, second-rate, etc. are 1640s, from British Navy division of ships into six classes based on size and strength. Phrase at any rate originally (1610s) meant "at any cost;" weakened sense of "at least" is attested by 1760.