Where did the expression "Rule of Thumb" originate from?

Question

This referred to a law back in the day when men were able to beat their wives w/ sticks to a certain extent.

But what did that expression have to do w/ that law?

Answer 1

The site listed below said that a man could beat his wife with a stick as long as the stick wasn't thicker than his thumb. Other interesting info there, too.

Thanks for asking this question. I didn't know that one at all.

Answer 2

The law stated that a man could beat his wife with a stick - but that the stick should be no larger than his own thumb. So theoretically, there was a limit to the damage he would inflict. These were different times.

But it would seem that explanation might be more of a myth - the expression is also said to be derived from English wood-workers. They would know their trade so well through experience that they wouldn't use rulers anymore. They would just place their thumb, or other finger where they wanted to cut and mark the wood there.

Answer 3

This is a complete myth. There was no such law. The origin of the phrase most likely relates to the practice in many trades, e.g. carpentry, to measure using the length or width of a finger when no more exact standard was needed. For a full explanation and thorough debunking of the domestic violence myth see:
http://www.canlaw.com/rights/thumbrul.htm