The X-factor in X

As Elon Musk rebrands Twitter and replaces its iconic bird logo with an X, here's unravelling the enigma of the 24th letter of the English alphabet

When German physicist Wilhelm Conrad Röntgen discovered a baffling new form of electromagnetic radiation in 1895, he named it “X-Rays”, using the mathematical designation “X” for something unknown. Fast forward 128 years, the once-mysterious letter is now the symbol of “everything”, at least in the view of Elon Musk, who just days ago rebranded Twitter and replaced its iconic bird logo with an X, as part of his vision to turn the platform into an everything app. For millions of Twitter users, now X marks the spot.

The letter X, for centuries, has been one of the most enigmatic characters in the realms of language, symbolism, religion, science, and even branding (SpaceX, Xbox, and Xerox to name a few). The 24th letter of the English alphabet (besides the numeral X) is unparalleled. But what makes it so fascinating?

According to many linguists, the origin of the letter X could be traced back to the Phoenician “samekh”, pronounced with a hard “s”. It took on a shape resembling a fish skeleton. For the Phoenicians, seafaring people from the eastern Mediterranean, the letter symbolised the importance of fishing and maritime trade in their culture. When the Greeks borrowed samekh around 9 BCE, it evolved into the Ionian letter “chi”, with a hard “k” sound. When the Romans adopted it for Latin (around the 3rd century), they altered its shape to X, with the “ks” sound used by those in western Greece.

The shape, on the other hand, is said to have its root in ancient Egypt, where a symbol resembling an X denoted an intersection. Among the Romans, X represented the numeral 10 —a sign of completeness and perfection. Later, when the Roman Empire adopted Christianity, X became a symbol of Christ, hence Xmas.

Showcasing the ever-changing nature of languages and expressions, this multicultural journey spanning centuries highlights the influences that helped evolve X into an enigmatic symbol from just a representation of a fish.

But how did X become an unknown variable? According to American polymath Terry Moore, “X is the unknown because you can’t say ‘sh’ in Spanish (cosmosmagazine. com).”

When the Arabic mathematical texts containing al-jabr (or algebra in English) reached Spain in the 11th-12th century, and Spanish scholars tried to translate them, Moore said, they encountered a challenge — the letter sheen with a sound “sh” and the words based on it, shay-un (meaning unknown thing/something) and al-shay-un (the unknown thing).

The word al-shay-un was peppered across the early Arabic mathematical texts, and those tasked with translating them into Spanish could not do so because of the lack of a letter sounding “sh”. They alternatively used the Greek chi. And when Spanish versions were translated into Latin, chi became X — the mathematical denotation of the unknown.

Later, French mathematician René Descartes popularised this convention by using x, y, and z for unknowns, and a, b, and c for known quantities in his La Géométrie (published in 1637). This usage is still ubiquitous in mathematical equations across the world.

Historians attribute the first use of the cross as a symbol for multiplication to William Oughtred, who in his Circles of Proportion (1632) wrote “x” to represent such a mathematical function.

Not only in mathematics, but X also represented the unknown in genetics. When Hermann Paul August Otto Henking, German cytologist, discovered the X chromosome in 1891, he dubbed it the X element; he was unsure whether it was a chromosome because of its unusual behaviour. Later, the X element became the X chromosome with the establishment of the fact that it was a sex-determining chromosome. When American geneticist Nettie Stevens discovered the male chromosome in 1905, she named it Y, following Henking’s “X” alphabetically.

X has had a mega impact on linguistics, too — from phonetics to abbreviations and slangs. It is often part of words that represent strength, intrigue, and a degree of mystery —box, extra, exit, excitement, and even sex. In abbreviations and acronyms, the letter serves a key purpose: XL (extra-large) and X-ing (crossing). X also has connotations with wrong, hence XXX for pornographic content. For long in text messages, XOXO represents kisses and hugs; in the world of gaming, the letter is often employed for “exit”.

In popular culture, we all know about Marvel Comics' superhero team X-Men, led by Professor Xavier. In space research, astrophysicists are still looking for Planet X, the hypothetical elusive ninth planet of the solar system — a rocky sphere 5-10 times the mass of Earth having an orbit about 20 times farther from the Sun on average than Neptune.

While the meanings and symbolism of X will keep evolving in sync with technological and cultural changes, the letter and its shape shall continue to inspire us to explore new worlds, ideas, and possibilities. For its versatility, X is the apt representation of “everything”, too.