Body Parts as Tools of Measurement

An online writer relating the history of luggage tells how in the old days, holiday makers didn’t try to manage with a mere suitcase when they went to the seaside for a week or so. They took the same kind of large trunks they would use if they were going on a long voyage:

…after all they had to change several times a day and not into dresses that barely covered their private parts but into foot-long petticoats and skirts. –Marie-Luise Stromer

I don’t think that a foot-long petticoat would cover much of a lady’s anatomy.

The writer was reaching for an expression to convey the fact that in those days, a woman’s dress extended all the way to her feet.

A choice of “foot-length” may not have been as jarring as “foot-long.” The reader could probably infer a meaning of “extending to the feet.”

The usual idiom for what the writer intended is floor-length.
Ex. She wore a floor-length gown.

The expression foot-long, on the other hand, means “a foot (12 inches) in length.”
Ex. They sell foot-long hotdogs here.

English possesses several measurement words that derive from body parts.

cubit – from Latin cubitum, “the elbow.” A cubit was a measurement based on the forearm from elbow to fingertip. The exact length varied according to whose arm was being used and could be from 18 to 22 inches.

digit – In Latin, digitus could mean either “finger” or “toe.” The same is true of digit in modern English. People use the digits of their hands to count to ten. And just think, we imagine we’re so modern and up-to-date because we live in a Digital Age.

fathom – Old English faethm was “the length of the outstretched arm,” about six feet. Water depth is measured in fathoms. Miners use the term to describe an area equal to six square feet.

hairbreadth – According to the Online Etymology Dictionary, hairbreadth is said to have once been a formal unit of measure equal to one-forty-eighth of an inch.

hand – Originally, a “hand” was a measurement of three inches, but now it is four inches. This measurement is stil used to reckon the height of horses.

handful – This is an indeterminate quantity of some dry measure, such as grain, that can be held in the cupped hand. A Greek word for “handful” is the origin of the Greek coin called a drachma.

span – In Old English a span was “the distance between the thumb and little finger of an extended hand,” roughly nine inches. Again, it all depended on whose hand.

thumb was probably the basis of the measurement now called an inch. We don’t measure things in “thumbs,” anymore, but we do talk about thumbnail sketches and thumbnails in the sense of “small images.”

The expression rule of thumb probably originated with carpenters who used their thumbs to take rough measurements. The notion that the expression originated with a law permitting a husband to beat his wife with a stick “no larger in circumference than his thumb,” has no historical basis.

NOTE: The article that triggered this post is interesting and, considering that the author may be writing English as a second language, extremely well-written.