Not only has the Twitter owner changed his profile picture to the new X logo and made his profile bio “X.com,” but the company’s official name is now X Corp., owned by the holding company X Holdings Corp., according to legal filings. Musk has been planning the X transformation since he acquired Twitter, saying he wants to create a digital town square where anything goes.

“Buying Twitter is an accelerant to creating X, the everything app,” Musk tweeted in October, shortly before he purchased the service for $44 billion.

The 24th letter has been a consistent presence in the billionaire’s business brandings and personal life for decades. In 1999, the tech magnate founded the original version of X.com, an online banking startup that eventually became PayPal, with three partners in Palo Alto, Calif. Eventually, Musk was ousted from the company in favor of Peter Thiel. 

Musk also has a child, born in 2020 with the musician formerly known as Grimes, named X Æ A-Xii (nicknamed X). In explaining the baby’s name on Twitter, Grimes said that X stood for “the unknown variable.” At Tesla, X is present, but only plays a supporting role. The Tesla Model X is one in a series of four cars, the S, 3, and Y. Together, they create the acronym S3XY—hardly a mathematical reference.

However, the Twitter rebranding harkens back to Musk’s beginnings as a businessman, and his history with the company now known as PayPal. Julie Anderson Ankenbrandt, an early PayPal executive, posted about the company’s naming on Quora.

“Elon, the other founders of the company that was x .com…and I sat around a backroom table at a long-defunct bar called the Blue Chalk in Palo Alto, trying decide what the name of the company should be… and the question at hand was whether to be q, x, or z dot com,” Anderson Ankenbradnt wrote in 2016. “Finally, when the waitress/female server brought the next round of drinks Elon asked her what she thought, and she said she like[d] x.com. Elon pounded the table and said “That’s it then!” and everyone laughed, but in the end that was pretty much how it was decided.”

Despite Musk’s 2000 ouster from X.com/PayPal, in which Thiel and his loyalists voted to change the company’s leadership and strip Musk of power while he was on a honeymoon in Australia, the Tesla CEO still has a soft spot for the early venture. Musk purchased the X.com domain from PayPal in 2017, at the time for purely nostalgic purposes.

He wrote in 2017 that he had “no plans” yet for the domain, but that it had “great sentimental value” to him. When another user tweeted at Musk suggesting that he use X.com as an “umbrella website” for all his other companies, Musk replied that that was probably the best use of the domain.

Now he seems to be realizing that vision by using Twitter’s existing structure as a launchpad for X as an “everything app” that will likely house multiple functions. It’s unclear whether many of the original Twitter features will survive, as Musk already intends to scrap other pillars of the network’s branding, according to his posts on the platform. Specifically, he tweeted that tweets should now be called “x’s” and that the concept of retweeting “should be rethought.” 

Twitter’s X-mutation may be an ambitious play to create a new, all-encompassing kind of online network—or it could be Musk’s way of licking wounds that even two decades and billions of dollars haven’t numbed.