Consider your phone. Is it an iPhone X? Maybe you're in deep on some bitcoin and compulsively checking the price of XɃT. Maybe you woke up today in a cold sweat, excited to watch your first XFL game. Notice anything all these things have in common? Yes. Very good. It's the letter X.

What is it about the letter X that promises the be-all and end-all of cool? SpaceX. The X Men. Generation X (disputably). X-ray goggles (definitely). The X factor (in general, not the show). Until as late as 1806, there were no words in the dictionary that began with the letter X. Today, we see X pinned to any number of products as a sign of some undefined cachet — the mystery of what something you buy, or buy into, can do for you. But what exactly are all these Xs trying to tell us? And, after all these years, are we any closer to knowing the answer?

The letter X has long acted as a symbol for something more meaningful. The French philosopher and mathematician René Descartes use of the letter as one of three glyphs to represent "unknown quantities" in equations is one of the first recorded examples of its cross-utility. Beyond math, an X came to be used to denote a kiss, a signature, or a place on a map where buried treasure is located (although the phrase "X marks the spot" was first used by Chicago gangsters).

According to Jack Chambers, a professor of linguistics at the University of Toronto, it's the letter's sheer simplicity that's allowed it to be so malleable. "For one thing, it is an elemental sign," Chambers wrote to me in an email. "[It's just] two intersecting straight lines, bilaterally symmetrical, dividing its space into quadrants."

What is it about the letter X?

But just because something is "elementary" in this sense doesn't explain its ubiquity. Aesthetics are just one piece of the puzzle. Chambers told me that the Christian tradition, viewing the letter as something resembling the cross, used it not only as a letter in words but as a symbol for the cross, and Christ, itself (think of, of course, the X in Xmas). Eventually, this symbolic representation secularized itself over time to seep into our own speech patterns. "X is now routinely read as the word 'cross' in compounds," Chambers said. "Railway X-ing, pedestrian X-ing, deer X-ing, turtle X-ing, and in X-country running and X-country skiing — even in X-dressing."

But what of its seemingly magical ability to make anything futuristic and cool? "It evokes a sense of mystery," Isaac Hooke, the author of the sci-fi trilogy AI Reborn, among others, told me. "Agent X came to the door. X signed the paper. In the past, people who couldn't write, or who didn't want to reveal who they were, would sign their names as X. It makes you wonder who this X is."

This utility of the letter X circles back to its inherent mystery. It's at this crossroads where we can identify what, exactly, has made it such a popular letter for everyone from tech bros to Jesus.

Modern use of X can be traced to when marketers were faced with a new challenge — the computer. In the '60s, when personal computers entered the consumer space, branding was mostly adjectival and etymological; you could pretty easily figure out what a "refrigerator" or a "motor vehicle" or a "washing machine" did, even if you'd never seen one.

Those marketing standbys broke down when companies like IBM had to decide what to call the things that printed little punched pieces of paper and solved equations but had the power to do much, much more. The name for these machines almost had to be abstract, because what computer manufacturers were selling was the potential to solve some as-yet-unknown future problem. They could, conceivably, do whatever you wanted them to do — you just needed to find something to do with them first.

This need for abstraction pretty much set the stage for X's popularity across the tech world. Take, for instance, Alphabet Inc.'s division of what they have dubbed "moonshot products," which is called, succinctly, X. According to Astro Teller, who goes by the title of Captain of Moonshots at X, the name began as a literal placeholder for the company's more ambitious projects that didn't necessarily fit into any of the preexisting business lines. "Initially the X in 'Google [x]' was a placeholder, but over time it's become clear that 'X' is the perfect name for us as it captures the spirit of what we're trying to do," he said. "In algebra, X is used to represent the unknown and when you're taking on huge problems you have be willing to go out into the unknown and try radical new approaches."

Modern use of X can be traced to when marketers were faced with a new challenge — the computer.

Unfortunately, this abstraction sometimes glosses over practical concerns. The difference between the first wave of consumer electric cars manufactured in the early '90s, like GM's EV1 or the Chrysler TEVan, and the Tesla Model X is one of marketing. While in the case of the former, there's plenty of apocryphal tales about a murderer's row of oil industry titans convincing these companies to do everything in their power to make sure that as few people bought these cars as possible.

In contrast, Elon Musk at least wants everybody to know about his cool electric car that's going to change the world. And with this promise, Musk and his Model X are signifying some beyond that's intentionally at odds with his current manufacturing realities. They're instead selling us the hacker's utopia of a way to work around what's preventing our world from reaching its collective potential. Conveniently, these roadblocks all seem to be things that impede the march of capital, like unions or the obligation to shareholders to report on your company's performance in good faith.

Take a look at where we're finding these Xs. The one at the end of the newest iPhone conveniently comes just around the same time that industry commentators began to question whether Apple had lost its phone-making spunk. Even more jarring is XɃT — the ticker symbol for bitcoin, which sometimes feels like a real-time bizarro simulation of the dangers of financial speculation. If the peaks and valleys of an overhyped cryptocurrency don't make you skeptical, the multitude of stories about armchair investors losing their shirt on what's essentially an unregulated security just might.

So take an X with a grain of salt. While it may stand for a whole nebulous world out there that by design points forward, it doesn't seem to be pointing at anything in particular. When in doubt, ask a linguist, and he might just sign off his email "Xciting," like Professor Chambers responded to me when I first reached out to him on my quest for answers. And in true X fashion, maybe that's all we can hope to know right now.

Anthony Burton is a writer in Toronto.