Why is a ship's speed measured in knots?

Knot is a speed unit used in maritime and aviation. 1 knot is equal to 1 nautical mile recorded in 1 hour, that is 1852 meters. The history of using knots as a speed unit in maritime goes back much further. It is known that the sailors have used a tool called ship log to measure the speed of the ships since the 1600s. This system consisted of a piece of wood and a hourglass shaped like a triangle attached to the end of a rope. There were knots thrown equally spaced (about 14.4 meters) on the rope. While the ship was moving, the piece of wood at the end of the rope was thrown into the water from the back of the ship and the knots on the sea part of the rope were counted in a certain time interval (approximately 30 seconds) measured by the hourglass. For example, if 10 knots were counted in 30 seconds, the speed of the ship was expressed as 10 knots. 1 knot measured by this method was approximately equal to 1 nautical mile covered in 1 hour.