Grimes has revealed that she has changed the name of her daughter with Twitter's billionaire owner ex-partner Elon Musk to a symbol.
The Canadian musician, whose real name is Claire Elise Boucher, shares two children with Musk after welcoming son X Æ A-XII in May 2020 and daughter Exa Dark Sideræl in December 2021.
However, Grimes announced on Thursday that the on-off couple, who last split in March 2022, had changed their youngest child's name to '?', despite the Government not officially acknowledging the alteration.
Grimes wrote on Twitter : "She's Y now, or "Why?" or just "?" (But the government won't recognize that). curiosity, the eternal question, .. and such."
The update came as the mum-of-two shared a rare photo of the 15-month-old child on the social media platform.
Bird charity banned from Twitter for repeatedly posting woodcock photos'Y' was dressed in a red onesie with blonde spikey hair, with Grimes also wearing a similar outfit as she said her daughter was "channelling Goku" - a character from Japanese anime programme Dragon Ball Z.
She added: "(Normally we post her for her privacy but she's fairly unrecognizable here since shes channeling Goku or smthn)."
'Y' was born via surrogate in December 2021, which Grimes accidentally revealed in a Vanity Fair profile after the writer heard the baby's cries in the background.
The article says that Exa refers to the supercomputing term exaFlops, while Dark alludes to "the unknown".
"People fear it but truly it’s the absence of photons. Dark matter is the beautiful mystery of our universe," Grimes said.
The singer said she had wanted her daughter to be called Odysseus Musk, but the pair compromised.
Grimes had previously explained how the former couple came up with the unusual moniker for their first child.
"X, the unknown variable," ️Grimes began in her post. "Æ, my elven spelling of Ai (love &/or Artificial intelligence)."
"A-12 = precursor to SR-17 (our favorite aircraft). No weapons, no defences, just speed. Great in battle, but non-violent. A = Archangel, my favorite song."
However, the pair have differing ideas on how to pronounce the name.
Elon Musk cleared by jury of deceiving Tesla investors over 2018 tweets"It’s just X, like the letter X. Then A.I. Like how you said the letter A then I," Grimes responded to one fan.
And when Elon was asked how it was pronounced, he added: "I mean it's just X, the letter X, and the 'Æ' is pronounced, 'Ash.'"