Now used to refer to a convenient principle with a broad application not intended to be strictly accurate in every situation, the term “rule of thumb” first appeared in print in Sir William Hope’s The Compleat Fencing-Master in 1692. The phrase is thought to have originated with woodworkers who used the length of their thumbs, rather than rulers, for measurements. However, it is often erroneously claimed that the term originally referred to a law that limited the thickness of what? Discuss
Source: The Free Dictionary