Rate of knots

Traditionally, since the mid-17 century, ships’ speeds were always calculated in knots, and originally a rate of knots was simply a term for the speed of a ship, whatever that might be. From the mid-19th century, however, ‘going at a rate of knots’ was extended to mean moving at a fast speed, whether one was running or travelling on horseback, or later, travelling in motor cars. See also Knot.