Fast Mash

  • Fathom comes from Old English, fæðm, which meant “embrace” and “the length of outstretched arms” as far back as the early 800s
  • This length was approximately 6 feet (for the average adult male) and was used for sounding the depths of water by the 1600s; the figurative sense, “to get to the bottom of something,” appears around the same time
  • Fæðm is rooted in the Proto-Indo-European *pet-, “to spread out”
  • Petal, patent, pass, and pace are related to *pet

This week, I’m delighted to write in response to a request. My first request. My good friend’s lovely new wife was trying to recall the word for measuring underwater depth. “Fathom!” she exuberantly texted, asking me to focus on it for my next entry.

I’ve yet to meet a person who wasn’t curious about (or at least didn’t have an opinion about) words. Words–our great common denominator. Well, that and about 99.9% of our genome.

Anyways, let’s fathom fathom.


Today, fathom leads a mostly figurative life. We usually speak of trying to fathom a tragedy or a person’s unusual behaviors. More often than not, we talk about how we can’t: We describe things as unfathomable. True, now and again, we landlubbers recall that fathom is a technical measurement for the depth of water–6 feet or 1.8 meters, to be precise. The measurement lingers but has mostly been supplanted by feet or meters, if I’m not mistaken.

This development of the word strikes me as rather intuitive: Just as a fathom plumbs the depths of water, so we get to the bottom of a situation when we fathom it.

But why 6 feet?

Fathom took form from the Old English fæðm. The OED has evidence for the word as far back as the early 800s–yes, the 800s–when it primarily referred to the “bosom,” “embracing arms” or an “embrace,” a “cubit,” and the “length of the outstretched arms.” A cubit, if you call up your biblical memory, is an ancient measurement of the distance of the forearm between the elbow and the tip of the middle finger.

A fathom, then? *Stretches out arms, looks left, looks right.* About 6 feet. Six Vitruvian, chauvinistic feet. Isn’t it a little kooky, measuring arms with feet?

By the 1300s, fathom became a verb that could mean “to embrace” or “to encircle with extended arms.” By the 1600s, it was verb for sounding water. Take some rope–some line–and stretch your arms out fully. Cut it to size. Sink it in the water and, voila, you have a fathom-line. (Yes, I did entertain how sailors might have possibly probed the seas sideways. And this line business is where the whole knots thing comes into play, too.) Around the same time appears fathoms figurative sense: to get to the bottom or truth of something, to understand it completely. 

Fathom has many cousins in Germanic languages. Historical linguists believe they descend from the the Proto-Germanic *faþmaz or *faþmoz, meaning “embrace.” At the bosom of this form rests *faþ– or *feþ-, stemming from the older Proto-Indo-European *pet-, *pete-, or *pot-, “to spread out” or “stretch out.” Notice a classic example of Grimm’s Law: Proto-Indo-European p‘s and t‘s evolving into Germanic f‘s and th‘s, respectively. Compare Latin’s pater and English’s father.

The root *pet– has birthed some interesting kin:

  • Pass and its great, big, fat family (e.g., surpass, Passover), comes from Latin, passus (step, pace)
  • Pace is part of the Latin passus clan, rooted in the verb pandere (not to behave like a panda, but to stretch the leg, spread out); a pace was also a historical measurement
  • Petal ultimately flowers out of Greek petalos, “outspread,” “broad,” “flat”
  • Patent, both in sense of “obvious” and “exclusive rights to an invention,” comes from the Latin verb patēre (to lie open); a patent was originally “letters patent,” from the French for “open letters,” which conferred ownership rights from powers that be

At an Arm’s Length

The way we measure the world may have become increasingly scientific, but that doesn’t mean that our measurements still aren’t relative. In 1983, the International Bureau of Weights and Measurements decided, after all, that a meter “is the length of the path travelled by light in a vacuum during a time interval of 1/299,792,458 of a second.” And what is a second? A second is “the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom.”

Well, isn’t that just hyperfine? I think you get the relativity idea.

Certainly, we’ve become more sophisticated in what our measurements are relative to, but a quick survey of the English tongue turns up how often we size up the world relative to our bodies. A fathom is six feet deep. Six feet deep is well, six feet. Gossip is within earshot, treasure can be found 60 paces from palm trees. Horses win by noses. Even football fields and car lengths point back to an embodied anthropocentric frame of reference. Think also about digits. Or time, tracked by the passage of the moon, sun, planets, and stars as seen from our terrestrial vistas.

Or yet more essential: front and backahead and behind.

Fathom reminds us that the way our bodies experience world and the way our environments shape our experiences help organize the way we think–and thus talk–about it. Our languages are embodied. Our languages our environed. Fathom that.

Further Reading

For more on the metaphorical nature of language and embodied nature of cognition, I suggest Lakoff and Johnson’s (1980) Metaphors We Live By.

If you are interested in ways in which language may shape culture and perception, I recommend Guy Deutchser’s (2010) Through the Looking Glass.

For more on the philosophy of embodiment, I suggest Maurice Merleau-Ponty’s (1945) The Phenomenology of Perception.

m ∫ r ∫


7 thoughts on “fathom

    1. That’s funny. I, too, thought about how many nautical terms have been applied to aeronautics, and I also entertained “fathom” has a unit of cosmic measurement. I guess that’s what light-years and warp-speed is for, though. I wonder, though, if there are any examples in early science fiction of usages of “fathom” or “knot.”

      I did come across a proposal of “space” originating in the root *pet -, but the evidence seems tenuous at best. Origin is usually listed as unknown, but definitely deserves some more fathoming.


  1. Funnily enough, I found “space” listed as a cognate of πέταλο in my Greek etymological dictionary. I actually went to look at πλατύς, which is the source of “plate”, and got distracted by πέταλο on the way there. I was wondering whether “plate” was in any way connected to *pet-. I still think there might be some distant connection to the “spread out” sense.


  2. The Greek words I have derived from PIE *pet- are:
    πατάνη – pot, plate
    πέταλον – leaf
    πέταλος (Ionic: πέτηλος) adj – broad, flat
    πετάννῡμι vb – to spread out (sails/clothes)
    πέτασος – broad-brimmed felt hat (of Hermes, with large side-flaps)
    They all have a semantic sense of ‘broad’, ‘flat’, ‘spread’ etc. but I found a reference to a connected with PIE *pet- (British) English word: ‘pandy’ vb – to strike palm of hand with cane, strap? I only know this word in the unrelated Welsh sense ‘pandy’ (pân – ‘fulled-cloth’ + tŷ – ‘house’ pandy = ‘fulling mill’) I’ve never heard of it in the English sense of beating one’s hand with a cane?


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