Where does the speed term knots come from?

Answer 1

Before ships had instrumentation to determine their speed, sailors needed some way to estimate their speed and thus determine how far they had travelled for navigation purposes. Since the only useful point of reference was the sea itself, they would drop a 'chip log' into the sea. The chip log was a wooden panel attached to a line. The panel was weighted at one end so that it would float perpendicular to the surface of the sea and thus create drag. The line was knotted every 567 inches (47'3") and the number of knots that passed through the sailor's hand during a 30-second period (determined by a sand-glass) determined the speed the craft was sailing relative to the sea surface. One knot would therefore be equivalent to 1.85166 kph. Today, we use a 28-second period which equates to 1.852 kph.

The "knot" indicated speed was standardized to be equal to a nautical mile per hour, which matched the ship's speed with its position when not in a moving current.