The Tesla CEO and his girlfriend welcomed their baby boy, X Æ A-12 Musk, on Monday and the moniker is certainly a head-scratcher. On Thursday's episode of The Joe Rogan Experience podcast, Musk said it was Grimes who "mostly" came up with the unique name.

"First of all, my partner is the one that, actually, mostly, came up with the name," the SpaceX CEO shared. "Yeah, she's great at names."

When asked how to say the name, Musk replied, "I mean it's just X, the letter X. And then, the Æ is, like, pronounced 'Ash.' Yeah. And then, A-12, A-12 is my contribution."

Grimes, real name Claire Elise Boucher, seems to have a different interpretation of the pronunciation. When responding to a curious fan on Instagram, she said, "It's just X, like the letter X. Then A.I. Like how you said the letter A then I."

The Canadian singer previously explained the meaning behind X Æ A-12. Grimes noted "X" stood for "the unknown variable," while Æ, or AI, means "love &/or Artificial intelligence."

X Æ A-12 is the first child for Grimes, 32, and fifth for Musk, 48. The entrepreneur shares five sons with ex-wife, Justine. They lost their first child, son Nevada, to SIDS at just 10 weeks old.

When speaking with Rogan, Musk said he enjoys being a father later in life.

"I think it’s better being older and having a kid. I appreciate it more," he said. "Babies are awesome. They're awesome."

Musk and Grimes first stepped out together in 2018.