The Canadian singer, born Claire Boucher, was initially reluctant to reveal the couple's second child, nicknamed "Y", but during an interview at her home in Austin, Texas, Vanity Fair journalist Devin Gordon overheard a baby crying.
When asked if she had a new baby in her life, the futurist pop singer initially said she was not "at liberty to speak on these things" but then confirmed Y joined the family in December, and eventually shared her full name, reports The Guardian.
The on-again, off-again couple welcomed their first child, X - A-12 (pronounced "X AI Archangel" and nicknamed "X"), in May 2020.
Y is the second child for Grimes and Musk's eighth. His first child, son Nevada Alexander with former wife Justine Wilson, died at 10 weeks of sudden infant death syndrome (Sids) in 2002.
Grimes said that the name Exa refers to the supercomputing term exaFLOPS, or the ability to perform 1 quintillion floating-point operations a second. Dark, she said, represents "the unknown. People fear it but truly it's the absence of photons. Dark matter is the beautiful mystery of our universe".
Siderl is pronounced "sigh-deer-ee-el" and is a "more elven" spelling of sidereal, "the true time of the universe, star time, deep space time, not our relative earth time". The name also honors her favourite Lord of the Rings character Galadriel, who "chooses to abdicate the ring". (IANS)
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