Canadian singer Grimes made headlines earlier this month when she gave birth to her first child with billionaire Elon Musk. The couple revealed that they’d given the baby the name  X Æ A-12, which raised more than a few eyebrows.

After clarifying how to pronounce little X Æ A-12’s name and then tweaking it to fit with California naming laws (the 12 was changed to the Roman numeral Xii), Grimes has now revealed what she has nicknamed her son, and it’s surprisingly much less complicated than you might think.

Grimes, whose real name is Claire Elise Boucher, told Bloomberg that she’d taken to calling the baby “Little X.”

Little X was born on May 4, and Grimes explained his unusual name’s meaning on Twitter a day later.

The 32-year-old wrote the X stood for “the unknown variable,” “Æ” is her “elven spelling of Ai (love &/or artificial intelligence) and “A-12” stood for the precursor to her and Musk’s favourite aircraft. 

Grimes has also said she thinks the unique moniker “sounds like the name of the main character in the story” and that she is hoping the baby “vibes with that.”