What is the origin of the "rule of thumb?"

Answer by  jillou (114)

While the origin is unknown, it is accepted the thumb was used for measurement, (today's inch) and the words for thumb and inch are the same in many languages. Whether this measurement was for planting seeds, aligning things or something else is still unidentified. Today it is used to mean a rough idea or rule for doing something, an approximation.

Answer by  sean52 (86)

Surprisingly, the origin of "rule of thumb" is unknown at the current time to the world. It has been speculated before to might have possibly come from the thumb used for measuring.