The Unexpected Life of the Letter X | NPR

The letter X, seemingly simple in its form – two intersecting lines – carries a surprisingly complex history. More than just a symbol in algebra or a signature placeholder, its story winds through ancient Greek dialects, Roman numerals, religious iconography, and even the evolution of language itself. Understanding the origins and varied uses of X reveals a fascinating glimpse into how symbols acquire meaning and how those meanings shift over time.

From Ancient Sounds to Roman Notation

The story of X begins in ancient Greece, around 800 B.C. As linguist Danny Bate explains, the letter originated from different pronunciations in various Greek dialects. In one dialect, it represented a sound similar to the Scottish “loch,” while in another, it combined the sounds of “k” and “s.” This latter pronunciation, ks, is the version that made its way into the Roman alphabet, which ultimately became the foundation for the English alphabet we utilize today. NPR’s Word of the Week series details this linguistic journey, highlighting how the letter’s unique sound combination contributed to its somewhat unusual status within the alphabet.

In Latin, and subsequently English, the ks sound typically appears at the end of syllables, rather than the beginning, which explains why so few English words actually *start* with X. Words like “xylophone” and “xenophobia” are exceptions, borrowed directly from Greek. This inherent limitation, the fact that X doesn’t easily fit into the typical flow of English pronunciation, may contribute to its enduring mystique.

A Symbol Beyond Language

The power of X extends beyond its phonetic value. Its simple, crossed form makes it a potent symbol, even in contexts where literacy isn’t a factor. Historically, X was used as a substitute for signatures by those unable to write, and it marked the quality of liquor barrels. This visual strength is likely rooted in its origins as a Roman numeral for 10. The system of Roman numerals likely predates their written form, starting with simple lines representing numbers, with crossing lines at 10 forming an X. A study published in the Journal of the History of Mathematics details the evolution of these numeral systems.

The Romans also employed X in a more somber context: St. Andrew the Apostle is traditionally believed to have been crucified on an X-shaped cross. This association with sacrifice and faith adds another layer to the letter’s symbolic weight.

X as Abbreviation and the Rise of the Unknown

Over time, X became a convenient abbreviation, particularly in religious contexts. The use of “Xmas” for Christmas, for example, dates back to at least the 11th century, with X representing the Greek letter Chi (Χ), the first letter of Christós. Etymologist Jess Zafarris, author of Useless Etymology, explains this historical linguistic shortcut.

Perhaps most significantly, X came to represent the unknown. This association was solidified in the 17th century by the philosopher and mathematician René Descartes, who used x, y, and z to represent unknown variables in his algebraic equations. This convention cemented X’s role as a placeholder for the undiscovered, a concept that has resonated far beyond the realm of mathematics.

Commercial Appeal and Modern Usage

The distinct visual form of X, combined with its association with the unknown, has also made it appealing for commercial purposes. Advertisers recognized that X “jumps out on the page,” as Harper puts it, and began incorporating it into brand names like Kleenex, Terminix, and Xerox. The most famous example, Xerox, arguably owes much of its brand recognition to the striking simplicity of its name.

More recently, X has found a place in the tech world, becoming shorthand for “experience” in terms like UX (user experience) and CX (customer experience). This adoption reflects the letter’s continued ability to convey a sense of innovation and forward-thinking.

The Enduring Appeal of a Singular Letter

From its ancient Greek roots to its modern-day applications, the letter X has proven remarkably adaptable. It’s a letter that has “always kind of had to fight to be used,” yet its unique history and symbolic weight have ensured its continued relevance. As Bate suggests, there’s something inherently compelling about X – a certain “vibe” that sets it apart from the other letters of the alphabet. Whether it represents the unknown in an equation, a signature on a document, or a brand name on a product, X continues to capture our attention and spark our imagination.

The story of X is a reminder that even the most basic elements of language – the letters we use every day – have rich and complex histories. It’s a history that reflects the evolution of human thought, culture, and communication. And as long as there are unknowns to explore and ideas to express, the letter X will likely continue to hold a special place in our collective consciousness.