Elon Musk has explained the meaning behind the baby name he and Grimes bestowed upon their newborn son, X Æ A-12 Musk, during an appearance on Joe Rogan’s podcast.

The interview, which aired Thursday, began with Rogan congratulating the Tesla CEO on the 4 May birth of his son - before asking Musk how to pronounce the name.

"How do you say the name?" Rogan asked. "Is it a placeholder?"

In response to the question, Musk explained that Grimes was the one who had “mostly” come up with the unique name.

“First of all, my partner is the one that, actually, mostly, came up with the name,” the 48-year-old began, adding: “Yeah, she’s great at names,” when Rogan interjected his congratulations.

“I mean it’s just X, the letter X,” Musk continued. “Um, and then, the Æ is, like, pronounced ‘Ash’.

“And then, A-12, A-12 is my contribution,” the SpaceX founder said as Rogan laughed. “Archangel 12, the precursor to the SR-71, is the coolest plane ever.”

After Rogan acknowledged that he didn’t know the plane, Musk explained that the SR-71 came from the CIA program called Archangel.

“Oh wow, what a dope looking plane,” Rogan said as he looked up photos. “Oh, okay, I get it.”

Grimes, 32, whose real name is Claire Elise Boucher, first broke down the meaning of the name on Twitter on Tuesday, where she explained that “X” stands for the “unknown variable,” Æ is “my elven spelling of AI (love and/or artificial intelligence),” and A-12 refers to her and Musk’s “favourite aircraft”.

The singer also said the “A" in the name represents "Archangel," which she said was her favourite song.

During the interview with Rogan, Musk, who shares five sons with his ex-wife Justine Wilson, also opened up about what it has been like having another child.

“Actually I think it’s better being older and having a kid,” the tech billionaire said. “I appreciate it more.

“Babies are awesome.”

While both Musk and Grimes have now offered explanations behind the meaning of their child’s name, neither has confirmed how to pronounce the series of symbols.

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