You have probably heard the expression Rule of Thumb once or twice in passing. Rule of Thumb is a phrase that refers to a method, procedure or even measurement that is taken based on common sense instead of a scientific process.
So for example, if you were cooking rice and measured the amount of salt by putting a drop of the water in your tongue, you are effectively checking the amount of salt by rule of thumb. It’s an easy enough expression to remember, so go ahead and incorporate it into your speaking or writing.
One thing though, the expression has been rumoured to have some pretty dark origins.
The English Wife-Beating Law
The expression Rule of Thumb has been said to be derived from a law that used to exist in England. According to that law, a man could beat his wife as long as the stick that he used was only as thick as his thumb.
Although, men were legally allowed to beat their wives in “moderation” during those times, the thumb rule has actually never existed.
Instead, the expression traces its real roots to the 1600s when during construction projects, tools were not readily available as … well, body parts were. This lead to people to people using their thumbs as a convenient way to quickly measure something.