Grimes and Elon Musk (Photo: John Shearer/Getty Images)

XÆ A-12 is officially a big brother.

Grimes and Elon Musk secretly welcomed a second child—a baby girl they nicknamed Y—in December 2021, via a surrogate, the musician told Vanity Fair.

Their daughter’s full name is Exa Dark Sideræl Musk, “Exa” being a reference to a supercomputing term and “Dark” representing “the unknown” and the “dark matter [that] is the beautiful mystery of our universe.” Sideræl, meanwhile, nods to her favorite Lord of the Rings character, Galadriel. Still, Grimes revealed that she was originally fighting for the name Odysseus. “I was fighting for Odysseus Musk,” she told the magazine. “A girl named Odysseus is my dream.”

The two welcomed their first child, a baby boy they nicknamed X, in May 2020. Pregnancy complications with X helped drive the decision to use a surrogate this time around.

“He was pressing on my nerves, so I kept collapsing,” Grimes recalled of her first pregnancy. “I took a few steps and collapsed. It was kind of scary, because you don’t want to fall a lot when you’re eight months pregnant. So I would just crawl to the bathroom and crawl back or whatever.” At one point, she said she thought she was dying. “Like, I hemorrhaged. It was scary.”

Despite welcoming a second child together, Grimes is still cryptic when it comes to clarifying her relationship status with the Tesla CEO. (The two reportedly split last September.)

“There’s no real word for it,” she said. “I would probably refer to him as my boyfriend, but we’re very fluid. We live in separate houses. We’re best friends. We see each other all the time. … We just have our own thing going on, and I don’t expect other people to understand it.”

This article originally appeared in Harper’s BAZAAR US