The billionaire Tesla CEO replied to one of his Twitter followers to reveal that Grimes was in labour.
When asked to reveal the name of his son, Musk tweeted: “X Æ A-12 Musk.”
At first it was not clear if Musk was joking about the name, or if he was being cryptic. It later turned out he was being serious.
After the name was announced, speculation arose that it might fall foul of the law in California, where the couple live, as names can only use the 26 alphabetical characters of the English language, according to the state constitution.
Grimes then confirmed that they had changed the name to “X Æ A-Xii”, adding: “Roman numerals. Looks better tbh.”
Explaining the meaning behind the name, Grimes said “X” stands for “the unknown variable”. Meanwhile, “Æ” is the Elven spelling of AI, which is shorthand for artificial intelligence and the word for “love” in several languages, such as Japanese.
“A-12 = precursor to SR-17 (our favourite aircraft). No weapons, no defenses, just speed. Great in battle, but non-violent,” she added. The “A” in the name also represents “Archangel”, the title of a song by Burial that she has previously described as her favourite.
Grimes and Musk seem to have different ideas of how to pronounce the name. “It’s just X, like the letter X. Then AI. Like how you said the letter A then I,” Grimes said.
Musk, meanwhile, told podcast host Joe Rogan: “I mean, it’s just X, the letter X. And then, the Æ is, like, pronounced ‘Ash’... and then, A-12, A-12 is my contribution,” he said.