Grimes has seemingly changed her and Elon Musk's daughter's name to Y.

While responding on Twitter to a fan's comment about a recent baby picture she posted of her daughter, the Oblivion singer revealed that she had changed the child's name.

"She's Y now, or Why? or just ? (But the government won't recognize that)," Grimes tweeted of her daughter's name. "curiosity, the eternal question... and such."

The singer - whose real name is Claire Boucher - welcomed the baby with Elon via surrogate in December 2021. The pair originally called her Exa Dark Sideræl Musk.

At the time, Grimes told Vanity Fair that she and Elon called the child Y as a nickname, though her recent tweet seemingly indicates a more official name change.

In the baby picture, Grimes and her daughter sported matching red onesies and neon yellow hair. The post was captioned "Y" for her daughter and "C" for herself.

Previously, Grimes told Vanity Fair that C was her nickname, standing for the speed of light.

In a follow-up tweet explaining the picture, she wrote, "Normally we post her for her privacy but she's fairly unrecognizable here since she's channelling Goku or (something)."

Grimes and Elon, who dated between 2018 and 2022, also share a two-year-old son named X Æ A-Xii.