attends the Heavenly Bodies: Fashion & The Catholic Imagination Costume Institute Gala at The Metropolitan Museum of Art on May 7, 2018 in New York City.

Grimes and Elon Musk are the parents of two. In a new interview, the singer revealed she and the Tesla founder secretly welcomed another baby – this time, a girl – in December 2021 via surrogate. 

Speaking with Vanity Fair, Grimes, who is also mum to 22-month-old son X Æ A-12 with Musk, whose name went viral back when the pair first announced it, revealed their second baby’s full name is Exa Dark Sideræl, though they’ve nicknamed her simply Y to match their firstborn’s nickname, X.

She also revealed was “fighting” to name her daughter Odysseus Musk, because “A girl named Odysseus is my dream,” but eventually she and Musk settled on Exa Dark Sideræl instead. She explained ‘Exa’ refers to a supercomputing term, exaFLOPS, while Dark represents “the unknown.” 

“People fear it but truly it’s the absence of photons. Dark matter is the beautiful mystery of our universe,” Grimes said. 

Sideræl, the third part of Y’s name, which is pronounced “sigh-deer-ee-el,” Grimes said is “a more elven” spelling of sidereal, which she defined as “the true time of the universe, star time, deep space time, not our relative earth time.” Sideræl is also a shoutout to her favourite Lord of the Rings character, Galadriel, who “chooses to abdicate the ring.”

Not only is the news of a second baby a surprise, but so too is the fact that Grimes and Musk are still dating. The pair announced their split in September 2021 after three years together but quietly reunited on their own terms last year. 

“There’s no real word for it,” Grimes said when trying to define their relationship. “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.” 

She added the situation works well for them and they’re the happiest they’ve been to date. “This is the best it’s ever been. … We just need to be free.” Plus, the pair plan on having more children too: “We’ve always wanted at least three or four.” Let me guess, Z is next?