Elon Musk and Grimes welcomed baby boy X Æ A-12 on May 4
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Grimes, Elon Musk
Grimes (L) and Elon Musk
| Credit: Taylor Hill/Getty Images

It seems like Elon Musk and Grimes may not see eye-to-eye when it comes to how to correctly pronounce their son's unique moniker.

Although the Tesla CEO, 48, offered up his own explanation about son X Æ A-12’s name last week, the 32-year-old singer had a slightly different answer when asked by a fan on social media.

“It’s just X, like the letter X,” she wrote on Thursday inside the comments section of a recent Instagram post.

“Then A.I.,” she added. “Like how you said the letter A then I.”

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Grimes
Grimes responding to a fan on Instagram
| Credit: Grimes/Instagram
Elon Musk Twitter
Elon Musk and Grimes's son, X Æ A-12
| Credit: Elon Musk Twitter

However, Musk didn’t appear to get the pronunciation memo.

During Thursday's episode of The Joe Rogan Experience podcast, Musk said that X is spoken "like the letter" while "the 'Æ' is pronounced like 'ash.' "

Giving credit where credit is due, he shareed that his girlfriend was actually the one who "mostly came up with the name,” although he did make a key contribution.

"A-12 was my contribution," the Space X founder said, explaining that he wanted to pay homage to the Lockheed A-12 reconnaissance aircraft built by the United States Central Intelligence Agency. "The Archangel-12, the precursor to the SR-71, the coolest plane ever."

Elon Musk Twitter
Elon Musk and son X Æ A-12
| Credit: Elon Musk Twitter

Giving fans some insight into what their son’s name meant, Grimes, whose birth name is Claire Boucher, previously explained that X represents “the unknown variable” and "Æ, my elven spelling of Ai (love &/or Artificial intelligence).”

She went on to share that part of her newborn's name is a nod to the CIA's Lockheed A-12 reconnaissance plane, which has “no weapons, no defenses, just speed. Great in battle, but non-violent.” The "A" in the name also represents "Archangel" — which she said is her "favorite song" — while the number "12" stood for the Chinese zodiac sign of the rat.

The child is the first for Grimes while Musk has five sons from a previous marriage. His first son, Nevada, died tragically of SIDS at 10 weeks old in 2002.

RELATED VIDEO: Elon Musk Shares First Photos of New Son with Grimes

Pronunciation aside, while the child’s name isn’t technically illegal, a family law attorney recently told PEOPLE that it won't be accepted by the state of California.

"In California, you can only use the '26 characters' of the English language in your baby name," David Glass said Wednesday. "Thus, you can't have numbers, Roman numerals, accents, umlauts or other symbols or emojis.”

Glass said that if X Æ A-12's birth certificate is submitted as-is, it is sure to be rejected and that the couple will "have an opportunity to appeal the rejection of the birth certificate application but it's unlikely that it will be granted."