Thumb As Measurement Device
The term is thought to originate with wood workers who used the width of their thumbs (i.e., inches) rather than rulers for measuring things, cementing its modern use as an imprecise yet reliable and convenient standard. This sense of thumb as a unit of measure also appears in Dutch, in which the word for thumb, duim, also means inch. The use of a single word or cognate for "inch" and "thumb" is common in many other Indo-European languages, for example, French: pouce inch/thumb; Italian: pollice inch/thumb; Spanish: pulgada inch, pulgar thumb; Portuguese: polegada inch, polegar thumb; Swedish: tum inch, tumme thumb; Sanskrit: angulam inch, anguli finger; Slovak: palec, Slovene: palec inch/thumb, Czech: palec inch/thumb.
Another possible origin of the phrase comes from measurement, in particular in agricultural fields. The plants need a fairly precise depth to seed properly, whether planted from seed or being replanted, but the depth can sometimes be estimated using the thumb. That is, a rule "(measurement) of thumb." According to Gary Martin, "The origin of the phrase remains unknown. It is likely that it refers to one of the numerous ways that thumbs have been used to estimate things—judging the alignment or distance of an object by holding the thumb in one's eye-line, the temperature of brews of beer, measurement of an inch from the joint to the nail to the tip, or across the thumb, etc. The phrase joins the whole nine yards as one that probably derives from some form of measurement but which is unlikely ever to be definitively pinned down."
Another theory is that the coarseness of ground flour produced by windmills in England was assessed by the miller rubbing it between his thumb and forefinger.
Read more about this topic: Rule Of Thumb
Famous quotes containing the words thumb, measurement and/or device:
“Your small hands, precisely equal to my own
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I could trust the world, or in many hands like these,
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or touching a human face ...”
—Adrienne Rich (b. 1929)
“Thats the great danger of sectarian opinions, they always accept the formulas of past events as useful for the measurement of future events and they never are, if you have high standards of accuracy.”
—John Dos Passos (18961970)
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—Joseph ODonnell. Clifford Sanforth. Professor James Houghland, Murder by Television, just before he demonstrates his new television device (1935)