In a Word: Common Words You Didn’t Know Were Also Units of Measure

You’ve measured things in feet, pounds, and grams, but what about barns, crabs, and nibbles?


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Managing editor and logophile Andy Hollandbeck reveals the sometimes surprising roots of common English words and phrases. Remember: Etymology tells us where a word comes from, but not what it means today.

In elementary school, teachers taught us about inches, feet, and miles; pounds and ounces; and minutes, seconds, and hours. And though we did learn the following words at the same time, they didn’t teach us that they were also specialized units of measure.

Barn (area)

In 1942, Marshall Halloway and Charles Baker were two physicists working on the Manhattan Project. Particle physics was a new discipline at the time, which meant that some of the concepts of dealing on the subatomic level were still being worked out and named. Halloway and Baker, over dinner one night, were brainstorming what they could call the typical nuclear cross-section — not literally the area of a bisected particle, but the effective target area that a nuclear particle represents in a collision. They came up with the barn.

Though a barn by human standards is insanely small, 10-24 cm2 (that’s 0.0000000000000000000000001 square centimeters), in particle physics, it’s relatively large. Some particles are as small as 10-21 barns, so getting these super-small particles to collide with a typical nuclear cross-section was, from a certain perspective, “like hitting the broad side of a barn.” Which is where they came up with the idea.

Because the Manhattan Project was highly classified, the existence of the barn as a unit of measure was also classified until 1948, and it’s still used today in nuclear and particle physics.

Cent (intonation)

Sure, you know that cent is a monetary unit — in more places than just the U.S. — but it’s also a unit of measurement in the world of music. In musical tuning, a cent is 1/100 of the interval between any two semitones. In layman’s terms: The range of possible tones between any two half-steps (adjacent notes on a piano) is divided into 100 cents. If two people played the same note on different instruments, and there was 5 cents or less of a difference between those notes, you might not notice a problem. But if one note was 10 cents or more higher than the other, it would sound out of tune — and unpleasant.

This cent, like the one you already knew, traces back to the Latin centum “hundred.”

Crab (radiation)

This unit is used for measuring the intensity of x-rays in space. The Crab Nebula from which it gets its name is a source of intense but fairly predictable x-rays, and it is used to calibrate other x-ray instruments in space. I’m no astrophysicist, but apparently the formula for calculating Crabs can result in some small numbers — much closer to zero than to one — so sometimes the milliCrab, one-thousandth of a Crab, is used instead.

Hand (height)

In many English-speaking countries, a horse’s height is still measured in hands. Originally based on the width of a human hand, it has since been standardized at 4 inches. Which makes this an odd-sounding but true statement: Three hands is a foot.

Hogshead and Butt (volume)

In the 14th century, a hogshead was simply a large cask or barrel, as one might use to make or transport beer or wine. Why it was called a hogshead is a mystery: It could have been a brand placed on the side of the barrel by an early maker, it could be connected to smaller wine flasks made from pig leather, or it could have just been a weird name that stuck. Regardless, the size of those barrels became a unit of measure. Today, a hogshead is equal to 63 gallons — but that isn’t the whole story. Over the last six centuries, the size of a hogshead has shifted not only from place to place, but based on what happy juice is being measured. For example, a hogshead of beer was larger than a hogshead of wine, which was larger than a hogshead of claret.

If you’ve got more than a hogshead of potables to share, you might have a butt. From the Old French bot “cask” and etymologically related to bottle, a butt is approximately two hogsheads — approximately because it, like the hogshead, has changed over time. This unit isn’t used as much as the hogshead today.

Nibble (digital data)

You’re probably familiar with the concept of a computer byte — it’s the basis of how we talk about computer storage space. One byte is made up of eight bits, the smallest unit of digital data, which is either a 0 or a 1. But computers don’t process bits individually — if you buy a decent laptop today, its operating system will probably be listed as a 64-bit OS. That means that it can process 64 bits (8 bytes) in a single step.

But that wasn’t always the case. Early computers couldn’t process data that quickly. In the early 1970s, the fastest computers used 4-bit processors — meaning they could process four bits, or half a byte, at a time. And that’s probably where the name came from: As David Benson, a Washington State University professor, remembered it, he had jokingly made a remark in 1958 about “half a byte” (i.e., “half a bite”) being a nibble, and the name stuck. So now, a nibble, sometimes spelled nybble to mirror the spelling of byte, is four bits.

Slug (mass)

Science and engineering disciplines these days have largely settled on using the International System of Units (SI) for measurement. These are the meters, grams, degrees Celsius, and other units of measure you’ll find in the average science classroom. But there are other systems.

One was called British Engineering Units, and to measure mass, it used the slug rather than the gram as a base unit. In this system, one slug is the mass that is accelerated by 1 foot per second per second when a net force of one pound is exerted on it, based on standard gravity. The short version: At the Earth’s surface, an object with a mass of 1 slug weighs 32.174 pounds.

The word slug was chosen sometime in the late 19th century by British physicist Arthur Mason Worthington based on the meaning “a block of metal,” not on the slimy garden invader. Mirroring the inch-foot relationship, 12 slugs is also referred to as 1 blob.

Fanciful Units

Many other units of measurement have been proposed over the years — sometimes humorously. Although they aren’t “official” in any way, they are still fun, and some of them have even found regular use. Here are some of my favorites:

  • Beard-second (distance): Inspired by the light-year, a beard-second is the length that an average beard grows in one second. It has been defined in the past as 10 nanometers, but Google Calculator uses 5 nm.
  • Mickey (distance): Early computer mouse developers needed a term to describe the smallest detectable movement of the hardware, so they borrowed the name of the most famous mouse. A typical mouse works at around 500 mickeys per inch, but super-sensitive mice (or mouses, your choice) work at over 15,000 mickeys per inch.
  • MilliHelen (beauty): Helen of Troy had “the face that launched a thousand ships.” If 1 Helen launched 1,000 ships, then 1 milliHelen is the level of beauty required to launch just one ship.
  • Smoot (length): In 1958, members of MIT’s Lambda Chi Alpha fraternity decided to calculate the length of Harvard Bridge using one of their pledges as a measuring stick. The pledge they chose was Oliver R. Smoot, who, years later, would become chairman of the American National Standards Institute. And they didn’t just do the math: Smoot would lie down on the bridge, progressing slowly across, with each Smoot being marked and each 10th Smoot labeled. Oliver Smoot was 5 feet 7 inches tall — now the length of 1 Smoot — and the bridge turned out to be 364.4 Smoots long, plus or minus one ear.

    Fast-forward to 1980, when the bridge was rebuilt: Cambridge police requested that the Smoot marks remain because they used them to indicate precise locations of incidents on the bridge. Like the beard-second, the Smoot is also a conversion option on the Google Calculator.

  • Warhol (fame): Andy Warhol is famous for saying, “In the future, everyone will be world-famous for 15 minutes.” By this standard, 1 Warhol equals 15 minutes of fame or hype. If you can manage to stay in the news for a week and a half, you’ve passed the kiloWarhol mark: 15,000 minutes, or 10 days and 10 hours.

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  1. Well, this is all new to me. In all honesty, if I’d brought up the measurement definitions of these otherwise singular meaning words, I might have found myself in a predicament of my teachers calling my mother yet again. Having said that, it’s best I’m learning of this now instead of then.


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