A Brief History of “X”

Yesterday, Apple unveiled the iPhone 8, iPhone 8 Plus, and iPhone X, which the company is pronouncing “iPhone Ten.” Ten years ago, Apple transformed the smartphone landscape—and our very lives, for better or worse—with its first very iPhone, hence the Roman numeral X, or 10, in its new mobile moniker. Let’s take a quick look at the history of X, from its birth as a letter and numeral to its spread into everything from Jesus to algebra.

The Roman Numeral X

As noted, X corresponds to the number 10 in Roman numerals. We know the ancient Romans adapted their notational system from the Etruscans, but the deeper roots of the symbols themselves are obscure.

One theory thinks the numerals evolved out of basic tally marks. The Roman numeral I (1) was a simple notch, with every fifth one double-notched, yielding V (5) and every tenth crossed into an X (10).

Another theory thinks the numerals emerged from hand-counting. I represents one finger and V a full hand. If you hold out your hand, you can see how the gap between the thumb and index finger might resemble a V. Hold out two hands for 10 and you can imagine how two V’s, stacked on top of each other, can look like an X.

Whatever their origin, the form of the symbols were adapted to the existing letters in the Latin alphabet—which included letter X.

Roman numerals marking a seating entrance in the Coliseum (Romewise). 

The Letter X

The ancient Greeks added letter X—called chi, its 22nd letter and our 24th—when they borrowed the Phoenician alphabet. Originally, X represented a kh sound, but certain regional alphabets took to using the symbol as a convenient shorthand for frequent ks combinations in the language. The Etruscans also adopted this convention—and later the Romans, which ultimately made its way into the sound and shape of English’s own X.

The Christ X

The Greek chi is the first letter in Χριστός (Khristos), source of Christ. This epithet literally means “anointed,” a translation of the Semitic messiah; rubbing oil on heads of kings, priests, and other important figures was an ancient custom used to consecrate them.

The second letter Χριστός is rho—ρ and source of r—and together Χριστός was abbreviated to its initial in old manuscripts. This digraph became the Christogram ☧, symbolizing Jesus on various Christian materials and imagery. The shorter shorthand of X for Christ also appears in Xmas, i.e., Christmas, which has been in use since the 1500s. That letter X also resemble a cross, so central to the Christian belief system, further underscores its association with Jesus Christ.

A chi-rho Christogram from a fourth-century sarcophagus (Wikimedia Commons).

The Kiss X

For Christians, Christ—and his symbol X—evoke faith and fidelity, and apparently medieval Christians, few of whom were literate, used X to sign documents as a token of their veracity.

This custom would also appear related to the modern use of X as a signature or in checkboxes, though we should never underestimate that this practice could just be because X is a distinctive and easy-to-form shape to make. Consider how we have X marks spots, dating to at least the early 1800s, which would seem to originate simply from, well, X marking spots.

Important documents were also sometimes signed with X and sealed with a kiss, and eventually the X-as-kiss emerged in letters and, now, text messages. The Oxford English Dictionary (OED) cites a letter by naturalist Gilbert White in 1763: “I am with many a xxxxxxx and many a Pater noster and Ave Maria, Gil. White.” Others think White’s X’s signified blessings, with an 1894 letter from Winston Churchill to his mother marking the earliest known use of the kiss X: “Please excuse bad writing as I am in an awful hurry. (Many kisses.) xxx WSC.”

The Algebraic X

X has been standing in for unknown mathematical quantities (variables) since the 17th century, a practice adopted from the French. The OED first cites it in English polymath (pun intended) Jonas Moore’s 1660 mathematical treatise, Arithmetic.

Why X? Contrary to a popular 2012 TED Talk, the OED offers:

The introduction of x, y, z as symbols of unknown quantities is due to Descartes (Géométrie, 1637), who, in order to provide symbols of unknowns corresponding to the symbols a, b, c of knowns, took the last letter of the alphabet, z, for the first unknown and proceeded backwards to y and x for the second and third respectively. There is no evidence in support of the hypothesis that x is derived ultimately from the mediæval transliteration xei of šay’ ‘thing’, used by the Arabs to denote the unknown quantity, or from the compendium for Latin res ‘thing’ or radix ‘root’ (resembling a loosely-written x), used by mediæval mathematicians.


The algebraic X is also responsible for the X in X-ray, a translation of the German X-strahlen (literally “X-beams”). German scientist Wilhelm Röntgen discovered them in 1895 and, taking a page from mathematics, so designated because he didn’t fully understand them.

The “unknown” X also produces that “indefinable quality” of the X-factor, which dates back all the way to the 1930s.

X’s sense of mystery probably led to X’s wide use in naming, from the X-Files to SpaceX, with X here conjuring up a sense of possibility, of wonder. Its associations with words like extreme and extra further lend it to so much branding (e.g., Xbox, Yukon XL, UberX). Names like Gas-X and Clean-X play with X as ex, or “former,” with X perhaps additionally calling up advanced technology, thanks to the letter’s “unknown” (read futuristic) resonances.

The unknown is also uncertain, which produces the X in Generation X, first used in the 1950s for a “generation of young people about whose future there is uncertainty.” Later uses of Generation X play upon valences of X as anxious or edgy for this supposedly disaffected post-Boomer population.

X is also a prominent sound in sex. Perhaps advertisers subliminally take advantage of this connection, but the XXX for pornographic content appears to come from the use of X for motion picture ratings for adult films. (I suspect the choice of X here prudishly alludes to the letter’s connotations with “wrong.”)

XXX, finally, was also used for the potency of various beers in the 19th century, likely leading to the trope of XXX for strong booze in cartoons.


Due to some upcoming wedding celebrations (I’m honored to be marrying my sister- and soon-to-be brother-in-law this weekend), Mashed Radish will taking Friday off.

m ∫ r ∫

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“Sequoia”: a giant-sized controversy

Earlier this week, heavy storms and flooding toppled the famous Pioneer Cabin Tree, a giant sequoia whose trunk cars once drove through, in California’s Calaveras Big Trees State Park. Before it was carved out in the 1880s to attract tourists, a forest fire had already hollowed out part of its trunk, apparently resembling a log cabin, hence the nickname Pioneer Cabin Tree. But why do we call this kind of tree a sequoia?

The Pioneer Cabin Tree, also known as the Tunnel Tree, in 2006. Image courtesy of Wikimedia Commons

American originals

In 1847, Austrian botanist Stephan Endlicher, while reorganizing and reclassifying plant species at the University of Vienna, created a new genus, which he called Sequoia. Endlicher’s Sequoia originally referred to redwoods, a close cousin to what we now know as and call the giant sequoia, or Sequoiadendron giganteum.

The common and long-running explanation is that Endlicher chose Sequoia to honor Sequoyah (1770-1843), a Tuskegee-born Cherokee silversmith who invented the Cherokee syllabary, which allowed for reading and writing in his native Cherokee tongue. Put simplistically, a syllabary uses written symbols to represent all the different syllables in a language, whereas an alphabet uses symbols to stand for all of the individual sounds. In Cherokee, for instance, Sequoyah wrote his name ᏎᏉᏯ, each symbol standing in for the syllables making up his name: Se-quo-ya. Sequoyah’s name comes from the Cherokee, Sikwayi, whose meaning and origin is unknown.

Sequoyah’s invention is a truly impressive, rare, and consequential feat, but author Gary Lowe thinks this etymology is quite the tall tale. Endlicher doesn’t mention Sequoyah anywhere in his papers and notes, but he was a philologist, including publishing a linguistic text on Chinese. Lowe ultimately roots the Sequoyah origin to an anonymous submission of an article in an 1856 edition of the agricultural magazine, The Country Gentleman. The author associates the name Sequoia with Sequoyah, for whom he concludes, approvingly, the giant tree was named. Subsequent writers and editors took up, and spread, this association, assuming Endlicher intended the name on the basis of his linguistic reputation. And so the explanation stuck.

One after the other

Lowe thinks Endlicher actually named Sequoia after the Latin verb sequor, to follow, source of words like sequence. Two other botanists, in fact, looked to the same sequor in the late 19th-century. The first suggested Endlicher picked Sequoia because the name followed in sequence after its original genus name, Taxodium; the second because redwoods followed after its extinct forbears. Lowe, rather, concludes Endlicher supplied Sequoia because the number of seeds its cones produce completes a larger sequence relative to those in its scientific suborder. 

Among giants

As far as the record is concerned, Europeans first encountered coast redwoods in 1769 – and the giant sequoia not until 1833. In the 1850s, British botanist John Lindley dubbed these trees Wellingtonia giganteum, honoring the Arthur Wellesley, the First Duke of Wellington, famed for his defeat of Napoleon at the Battle of Waterloo. “This sat poorly with the Americas,” as Doug Harper at the Online Etymology Dictionary diplomatically sums it up, though Wellingtonia persists in British English. French botanist Joseph Decaisne reclassified the tree under Endlicher’s Sequoia in 1854, and it wasn’t until 1939 that the American botanist John Bucholz determined giant sequoias were a distinct genus from the coast redwood. Bucholz nodded to Endlicher with his new name, Sequoiadendron giganteum. (Dendron comes from the Greek for “tree,” giganteum from the Greek for “giant.”)

Names aside, there is no controversy when it comes to the majesty of sequoias, reaching hundreds of feet in the air and spanning thousands of year in age. Perhaps we can honor the likes of Pioneer Cabin Tree more directly, more immediately, more simply, and look to a name the great American naturalist John Muir once used for the sequoia: Big Tree.

m ∫ r ∫

Easy as un-bi-tri? Naming new elements

Recently, the International Union of Pure and Applied Chemistry (IUPAC) added four new elements to the periodic table. They are temporarily known as ununtriumununpentiumununseptium, and ununoctium.

That’s a daunting lot of u’s, but the nomenclature behind them is actually pretty, um, elementary – which is about the only thing that seems simple when it comes to the business of chemistry, if you ask me.

Actually, even the naming can get pretty complicated, if you dig deep enough, but here’s a basic breakdown, with a little etymology mixed in.

The whys of all the u‘s 


Image from IUPAC.

Before receiving permanent names, new elements take on provisional ones, called “systematic names,” according to the IUPAC’s official guidelines.

These systematic names are based on the elements’ atomic numbers and derived from Latin and Greek roots for numerals.

Let’s take ununtrium. This is element 113, as the element has 113 protons. Ununtrium literally and sequentially links Latin roots for digits 1, 1, and 3. (As opposed to the Latin for one hundred and thirteen, which I believe is centum et tredecim, but don’t necessarily count on that).

And just to be clear, the Latin root for one is un-, from ūnus. For three we have tri-, formed on trēs.

Then, we tack on the suffix ium, used to name metallic elements. Indeed, these elements, completing the periodic table’s seventh row, are some truly superheavy, if incredibly short-lived, metals synthesized in the laboratory.

Now, the Latin words for many elements – like gold, or aurum, and iron, ferrum – end in –um. The Oxford English Dictionary observes that Cornish scientist Humphry Davy, who discovered a number of metals such as potassium and sodium, helped propel the -ium suffix back in 1807. Based on the compounds Davy was electrolyzing, potassium is formed on potash and sodiumsoda. And so from these –ium largely prevailed ever since.

Ununpentium follows the pattern but uses the Greek root for fivepent-, apparently to avoid confusion between Latin’s quad(for digit 4) and quint– (for digit 5).  Ununseptium and ununoctium continue with the Latin roots for seven (sept-) and eight (oct-).

And the temporary chemical symbols of the new elements– Uut, Uup, Uus, and Uu0 – simply abbreviate the initial letter of their component numerical roots. Easy as un-, bi-, tri-, right?

All this once made element 111, now officially roentgenium, quite the u-ful: unununium, with chemical symbol Uuu.

Name game, round 2

Next, the new elements’ discoverers will submit recommendations for permanent names to the IUPAC, which reviews them for suitability, especially for use across languages. According to the IUPAC’s guidelines, the new names must be based on a mythological concept or character, a mineral or similar substance, a place or geographical region, a property the element displays, or a scientist.

If recent discoveries are any measure, the new names will likely honor the laboratories or nationalities of the scientists. So, the Japanese scientists who synthesized ununtrium may submit japonium for the official name.

You can read the IUPAC’s official recommendations for naming new elements here. For more on the history of the IUPAC’s recommendations, I recommend this piece by Quartz. I also enjoyed the BBC’s take on how elements get their names. And for some more general information on the elements, head over to NPR.

Next post, we’ll look into the origin of the very word element, which turns out to be far from basic.

m ∫ r ∫