In seamen’s language, a “knot” is a division of the log-line serving to meas-ure the rate of the vessel’s motion. The number of knots which run off from the reel in half a minute shows the number of miles the vessel sails in an hour. Hence when a ship goes eight miles an hour she is said to go “eight knots.” webster
Source: Black’s Law Dictionary 2nd Ed (1910)
