…Musk says he chose x because it "embod[ies] the imperfections in us all that make us unique". His fascination with it dates back over two decades, first evident in 1999 when he named his online banking service X.com, before it later evolved into PayPal. He bought the web domain back in 2017, claiming it had "great sentimental value." He named an early Tesla car Model X, and his space exploration programme SpaceX. In 2020, Musk had a son with the musician Grimes, and the couple named him X Æ A-12 Musk…
https://www.bbc.com/culture/article/20230728-twitters-rebrand-why-x-could-be-the-most-powerful-letter-in-english