“Roman numerals,” Grimes wrote on Instagram. “Looks better tbh.”

Elon Musk and his girlfriend Grimes have changed their baby’s much publicised name. Earlier this month the pop star gave birth to Musk’s sixth child, X Æ A-12 Musk.

Appearing on “The Joe Rogan Experience,” new father Elon Musk broke down the name of his baby boy with Grimes, letter by letter, number by number and symbol by symbol.

“I mean, it’s just ‘X’ — the letter X — and then the A-E is, like, pronounced ‘ash,’” the Tesla chief executive told Rogan, who couldn’t help but laugh. “And then ‘A-12′ is my contribution … Archangel 12, the precursor to the SR-71 — coolest plane ever.”

Grimes later tweeted a full breakdown of the name:

“•X, the unknown variable

•Æ, my elven spelling of Ai (love &/or Artificial intelligence)

•A-12 = precursor to SR-17 (our favorite aircraft). No weapons, no defenses, just speed. Great in battle, but non-violent

+ (A=Archangel, my favorite song) (metal rat)”

However, the state of California laws only allow people to register baby names with the 26 alphabetical characters.

The change in the name came when an Instagram follower of the Canadian singer asked if she had considered changing the name of the child and she replied with, “X AE A-Xii.”

The singer also responded to another comment: “Roman numerals. Looks better tbh.”

Elon Musk already has five children. A notorious workaholic, he spends most of his free time in either the Tesla or Space X offices or in one of his several Los Angeles mansions.

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