• Tesla and SpaceX CEO Elon Musk and the musician Grimes have had their first baby, a boy born Monday night.
  • Musk has already caused confusion with the baby’s name, which he tweeted is “X Æ A-12 Musk.”
  • Twitter users were trying to guess what the string of characters means. One person said it stands for “X Ash Archangel,” which Musk liked on Twitter. Others guessed that the X related to the Bible book of Genesis or thought the name stood for “Jao.”
  • Grimes broke down the significance of each letter of the bizarre name on Twitter on Tuesday night, explaining that X stands for “the unknown variable,” Æ stands for “my elven spelling of Ai” and A-12 is the “precursor to SR-17 (our favorite aircraft).”
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The tech billionaire Elon Musk and the musician Grimes have welcomed their first child together, a boy born Monday night. Musk shared photos of the baby on Monday and confirmed that both Grimes and the baby were doing well.

But the Tesla and SpaceX CEO has already caused confusion over the baby’s name, which he tweeted was “X Æ A-12 Musk.”

While it’s not clear whether Musk was joking, many of his and Grimes’ fans have interpreted the name as something of a riddle, floating their best guesses for what the string of characters means.

One Twitter user interpreted the name as “X Ash Archangel” – “Æ” is pronounced “ash,” and “Archangel” was the internal codename for the CIA’s A-12 aircraft. Musk liked the tweet, leading people to believe it was the right guess.

https://twitter.com/flcnhvy/status/1257538193911623681?ref_src=twsrc%5Etfw

Another person guessed that the X related to Genesis, after the book in the Bible.

Another theory used some math to come up with the name: X is the Roman numeral for 10, J is the 10th letter of the alphabet, and if you count backward 12 letters from A, you get O.

As one person pointed out, if the baby's name is X, Musk already owns the domain name for it: In 2017, he bought back X.com, the website for his second company.

And if the name Musk tweeted is true, it may have been in the works for a long time. One person noted that the Latin character Æ also appears in a song from Grimes' latest album.

Grimes explained the significance of the name in a tweet on Tuesday night, breaking down each portion of the moniker.

"X, the unknown variable," she said. "Æ, my elven spelling of Ai (love &/or Artificial intelligence)."

She continued: "A-12 = precursor to SR-17 (our favorite aircraft). No weapons, no defenses, just speed. Great in battle, but non-violent." (It's possible she meant SR-71, not SR-17.)

She added that "A" also corresponds to "Archangel, my favorite song."

The clarification seemed to add more confusion, and many Twitter users questioned if the name was actually real.

"WAIT SO YALL WERENT JOKING???" user xovoz responded. "

"You realize this is a human child and not an EP right," wrote user mascdonna.

Musk and Grimes, whose real name is Claire Boucher, revealed they were dating in May 2018, almost exactly two years before their son was born. Musk has five other sons with his first wife, the author Justine Musk: twins named Griffin and Xavier and triplets named Damian, Saxon, and Kai.