log: [14] Log is a mystery word. It first turns up (in the sense ‘felled timber’) towards the end of the 14th century, but it has no ascertainable relatives in any other language. Nor is it altogether clear how the sense ‘ship’s record’ came about. It was inspired by the use of log for a thin piece of wood floated in the water from a line to determine the speed of a ship, but some etymologists have speculated that this is not the same word as log ‘piece of timber’, but was adapted from Arabic lauh ‘tablet’. [log etymology, log origin, 英语词源]