Elon Musk said his and Grimes' new baby is named X Æ A-12, and no one can figure out what it means. Here are the best guesses we've seen so far.

• Tesla and SpaceX CEO Elon Musk and 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 are 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 the X relates to the Bible book Genesis, or thought the name stood for "Jao."
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Tech billionaire Elon Musk and musician Grimes have welcomed their first child together, a baby boy born Monday night. Musk shared photos of the baby on Monday, and confirmed that both Grimes and the baby are doing well.

But the Tesla and SpaceX CEO has already caused confusion over the baby's name: "X Æ A-12 Musk," according to a tweet from Musk himself.

While it's not clear if Musk was joking or not, many of his and Grimes' fans have interpreted the name is 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 following tweet, leading people to believe it's the right guess:

Another person guessed 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 tenth letter of the alphabet, and if you count backwards to 12 from the letter "A," you get the letter 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 the domain X.com, which was the website for his second-ever company.

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

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