Elon Musk Reveals Who Came up With His and Grimes’ Son’s Name, X AE A-12

Elon Musk is revealing a little more about the origination of the unique name he and girlfriend Grimes gave to their newborn son: X Æ A-12. In Thursday’s episode of The Joe Rogan Experience podcast, the Tesla CEO revealed it was the “Genesis” singer who “mostly came up with the name,” praising, “Yeah, she’s great at names.”

According to Musk, the name is pronounced with X “like the letter,” while “the ‘Æ’ is pronounced like ‘ash,’” which comes in opposition with how Grimes explained the name was pronounced Thursday on Instagram, saying, “It’s just X, like the letter X. Then A.I. Like how you said the letter A then I.” However you pronounce the first part of the baby’s name, Musk told Rogan that the A-12 portion of the moniker was his idea in reference to the Lockheed A-12 reconnaissance aircraft built by the U.S. Central Intelligence Agency.

“A-12 was my contribution. The Archangel-12, the precursor to the SR-71, the coolest plane ever,” he explained. As for the other portions of the name, Grimes — whose real name is Claire Boucher — previously explained the X stood for the “unknown variable” and the Æ is her “elven spelling of Ai (love &/or Artificial intelligence).”

Musk and Grimes welcomed son X Æ A-12 on Monday, the first for the singer and the sixth for the SpaceX founder, who has five sons from a previous marriage. His first son, Nevada, died of SIDS at 10 weeks old in 2002. On Thursday’s podcast, Musk revealed he was loving being a father at 48. “Actually, I think it’s better being older and having a kid,” he said. “I appreciate it more. Babies are awesome. They’re awesome. They’re little lovebugs. It’s wonderful. It’s great.”

And while the couple’s interesting name choice has gone viral as people debate the true pronunciation, it likely won’t be the name permitted on the little boy’s birth certificate under California statute. David Glass, a family law attorney, told PEOPLE, “In California, you can only use the ’26 characters’ of the English language in your baby name. Thus, you can’t have numbers, Roman numerals, accents, umlauts or other symbols or emojis. Although an apostrophe, for a name like ‘O’Connor,’ is acceptable.”

While the name is not illegal, Glass said the couple would likely have their birth certificate rejected by the state. “They have an opportunity to appeal the rejection of the birth certificate application but it’s unlikely that it will be granted because, again, California … has been struggling with using symbols,” Glass added.