Elon Musk and Grimes have been known for their unconventional approach to naming their children, and their daughter, Exa Dark Sideræl Musk, is no exception. The couple welcomed her into the world privately through surrogacy, a fact disclosed by Grimes during a candid 2022 interview with Vanity Fair.

Grimes shared the inspiration behind their daughter’s unique name. “Exa” is a nod to the term “exaFLOPS,” which represents the capability to execute a staggering one quintillion floating-point operations per second, a fitting choice for the offspring of a tech mogul. Meanwhile, “Dark” symbolizes the enigmatic and often misunderstood aspects of the universe. “Dark matter is the beautiful mystery of our universe,” Grimes explained, highlighting the intrigue that surrounds the unknown.

The name “Sideræl,” pronounced “sigh-deer-ee-el,” carries a celestial significance. Grimes describes it as “the true time of the universe, star time, deep space time,” setting it apart from our earthly perception of time. Furthermore, it pays homage to her cherished Lord of the Rings character, Galadriel, who famously chooses to renounce the power of the ring.

Further insight into their family came from author Walter Isaacson in his biography, Elon Musk. He confirmed that the couple’s daughter, Exa, was born in December 2021 via surrogate, adding another layer to Musk and Grimes’ intriguing personal story.

Walter Isaacson revealed in his biography Elon Musk that Exa was born in December 2021 via surrogate.

The book also stated that around Father’s Day 2022, the on-again, off-again couple welcomed a child named Techno Mechanicus, nicknamed Tau, also via surrogate. The biography includes a photo, dated June 2022, of Elon feeding the baby boy.

Though Grimes would prefer other salient details be kept private. “I have tried begging the public and my kids dad to keep them offline, and I’ve tried legal recourse,” she shared on social media in 2025. “The state of my children’s lives being public is of grave concern to me and I think about how to solve this every day. It’s insane to me that theres no way to deal with this.”