In the 1400's a law was set forth in England that a man was allowed to beat his wife with a stick no thicker than his thumb Hence we have the rule of thumb -----------------------------------------?

Answer:
This is an urban legend. There was no such law. The phrase "rule of thumb" comes, rather, from the time-honored practice of using the thumb to make rough measurements (think "rule" as in "ruler"). In some languages, in fact, the word for "inch" is the same as the word for "thumb" (e.g., French pouce) or is derived from it (e.g. Spanish plugada, from pulgar).
First answer by Enlil. Last edit by Enlil. Contributor trust: 75 [recommend contributor recommended]. Question popularity: 12 [recommend question].