There are many curious phrases in the English language that we use everyday without thinking about what they actually mean. One such phrase is 'rule of thumb'.
What does it mean
Meaning A 'rule of thumb' is an estimated measure for something, not a scientific or exact mathematical measurement. It is said that the phrase came about from a judge's ruling in 1782, which said that wife's beating was fine as long as the husband did not use a stick thicker than his thumb. It seems however, that the judge who is alleged to have made the ruling, one Judge Sir Francis Buller, never actually made this ruling, and suffered ridicule and lampooning in cartoons for some years, after the alleged incident. First use The 'rule of thumb's origin is difficult to define exactly. The phrase was used in the 1600s, and first appeared in print in 1692, in a book about the art of fencing, or sword-play. It could be that the origin derives from the simple use of the thumb, as a rudimentary measure for things. Artists are often depicted holding their thumbs up in front of their eyes, to gauge distance and proportion. It is also been used in trades, such as carpentry.
Phrases related to the hand
There are many phrases related to parts of the hand, and sometimes, the meaning of the phrases are obvious, and sometimes, obscure. Hand The 'hand' is a measurement of horses from the top of its withers to the ground. It is generally accepted to be four-inches. It is believed that this measurement dates back to the time of the ancient Eyptians. Over the years, it has been either four fingers wide, or four fingers and included the thumb. Nowadays, the measurement has been standardised to make the matter simpler for all concerned. Finger Drinkers of Scotch Whisky (and some other alcoholic beverages) use the measurement of a 'finger'. This again is rather inaccurate, as it rather depends on the size of the hand, and therefore, the finger used in the measurement. It is generally thought to be around an ounce of whisky. If you like your whisky, make sure that the person pouring has fat fingers! Arm A popular phrase nowadays is 'arm candy', which means a particularly attractive person, whom someone takes to a special event to show how important or attractive they are. Most often, the 'arm candy' is only there for show, and has no real relationship with the person on whose arm they appear. Final word So, as a general 'rule of thumb', there are any number of phrases in the English language that have unlikely and unusual origins. No wonder, foreigners have trouble learning the language.