A log is a piece of wood. That is the origin of "log" meaning "journal".
It is nautical in origin. A ship's log was a device for measuring the speed of a ship through the water. The log was a "a thin quadrant of wood, loaded so as to float upright in the water, and fastened to a line wound on a reel". It was dropped over the side of the ship. It would float in a fixed position in rela
[nq:1]The line was allowed to unreel. The length of line that was unreeled in a particular time was a measure of the speed of the ship through the water.[/nq] And the line was knotted at fixed intervals. The length of line paid out was measured by counting the number of knots that went over the rail. Hence "knot" as a measure of speed.