Grimes Explained Why She and Elon Musk Named Their New Baby X Æ A-12

• Elon Musk announced that Grimes had given birth to their first child together on Monday, May 4.
• Musk later shared the baby's name: X Æ A-12 Musk.
• Grimes confirmed the name in a tweet Tuesday night, explaining that each element had personal significance to the couple.

Elon Musk announced the arrival of his first child with girlfriend Grimes on Monday, May 4, tweeting, "Mom baby all good." (Musk also has five sons from his previous marriage to Justine Musk.) He subsequently tweeted the newborn's name: X Æ A-12 Musk.

In Grimes' first tweet since the baby, her first child, was born, she confirmed the name, explaining each individual element and what it means to the couple. "X, the unknown variable," she tweeted. "Æ, my elven spelling of Ai (love /or Artificial intelligence)."

"A-12" is an military airplane reference, Grimes (real name Claire Boucher) explained. The Lockheed A-12 is a now retired reconnaissance aircraft built for the CIA in the 1960s. "No weapons, no defenses, just speed. Great in battle, but non-violent," Grimes tweeted. The aircraft was known as Archangel during development, according to the BBC—and "Archangel" also happens to be Grimes' favorite song, she added. (A little internet sleuthing indicates she's referring to "Archangel" by Burial.)

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