The Meaning and Origin of the Expression: Rule of Thumb
“Rule of Thumb” means: A way of estimating according to a rough and practical approach, instead of a true scientific or precise measurement.
A popular, but untrue, origin of the “rule of thumb” phrase is that it came into popular use from an old English law that allowed a man to beat his wife with a stick or switch, as long as it was no thicker than his own thumb.
Judge Sir Francis Buller, in the year 1782, is reported to have made a legal ruling containing the words “rule of thumb.” The following year, in 1783, James Gillray published a satirical cartoon that attacked Buller as “Judge Thumb.” The cartoon depicted a man beating a woman that was trying to run away in the background, with Buller carrying two bundles of sticks in the foreground. The caption on the cartoon read “or_ Patent Sticks for Family Correction: Warranted Lawful!”
Judge Buller was harsh in handing out his punishments and had a reputation for being very pretentious, but there is no actual evidence that he ever made this infamous ruling. Author of the 1870 book, The Judges of England, wrote that “no substantial evidence has been found that he ever expressed so ungallant an opinion.” At one time in history, however, there was indeed British common law that made it legal for a “man to chastise his wife in moderation” – the “rule of thumb” that made it legal for a man to beat his wife has never been law in England.
It is certainly possible that people started associating “rule of thumb” with wife beating due to this cartoon, but again, there is no evidence of a British law ever being in place that allowed a husband to beat his wife with a stick smaller than his thumb.
Even if society mistakenly thought the law did exist, there’s no reason to believe that anyone ever actually called it the “rule of thumb.” The phrase has been in common use since the 1600s and has appeared many thousands of times in print dating back to at least that timeframe. However, there are no records that associate the expression with domestic violence until much later in history, when the thought was made popular by feminists groups. The misconception that the wife-beating law was true was circulated greatly during the 1970s. This may have been influenced by a reemergence of Gillray’s cartoon or as a reaction to the 1966 The Rolling Stones’ song – “Under My Thumb.”
As stated above, the phrase itself has been in circulation since at least the 1600s. The earliest identified use of it in print appears in a sermon given by the English puritan James Durham, printed in Heaven Upon Earth in 1685:
“many profest Christians are like to foolish builders, who build by guess, and by rule of thumb, (as we use to speak) and not by Square and Rule.”
The exact origin of the phrase is unknown, although it is likely that it refers to one of the many ways that thumbs have been used throughout time to estimate distance or measurement. It is likely the phrase originated from carpenters who used their thumbs as a quick and handy measuring tool, either by holding it in front of their eyes in an attempt to gauge longer distances or because the average thumb is approximately one inch across.
As a general rule of thumb, I do not go out on weekday nights.
A good rule of thumb is that a student attend every class.
The general rule of thumb is that most basketball games are played at night.
A good rule of thumb is to jump in water feet first.