Billie Eilish's name is recognized all over the world thanks to her chart-topping music career – but her well-known moniker is, in fact, her stage name.
The 22-year-old was given a much longer name by her parents Maggie Baird and Patrick O'Connell, and Billie wasn't even supposed to be her first name.
Just before her birth on December 18, 2001, the Bad Guy singer was affectionately called 'Pirate' by her then four-year-old brother, Finneas, who was going through a pirate phase.
However, as her mother was reaching the end of her pregnancy, Billie's grandfather died and they opted to name her after him instead.
"They called me pirate for months, and they were kind of planning on naming me Pirate," Billie said in her eponymous first book in 2021.
"And soon before I was born, my grandfather died, and his name was William, AKA Bill, Billie. And that's where my name came from," she explained.
'Pirate' wasn't completely forgotten though and transitioned to become one of Billie's middle names alongside her mother's maiden name, making her full name Billie Eilish Pirate Baird O'Connell.
While 'Pirate' was supposed to be her main middle name, Billie revealed to the BBC in 2017 that her uncle put his foot down, so Eilish – inspired by a conjoined twin her parents saw in a documentary – became her middle name.
She explained: "[Eilish] is my middle name. So, I'm Billie Eilish Pirate Baird O'Connell. Pretty weird, right? Pirate was going to be my middle name, but then my uncle had a problem with it because pirates are bad. Then Baird is my mother's name."
Despite all her names, Billie chose to use her middle name 'Eilish' as her stage name, admitting in 2023 that she opted against adding her surname because it sounds "very Irish".
"It's like very, very Irish. Billie Eilish O'Connell, it doesn't get more Irish than that," she said on Jimmy Kimmel Live.
Her brother and collaborator Finneas agreed and said that he dropped 'O'Connell' from his stage name because it felt "clunky".
Meanwhile, Billie is gearing up to go on tour after announcing her Hit Me Hard And Soft tour in April.
Named after her latest album, it kicks off in North America in September before heading to Australia in February 2025, and then across Europe from April.
The tour will partner with the plant-based food organization Support + Feed – an initiative founded by her mother – and environmental non-profit organization REVERB.
According to promoters Live Nation, the shows will also aim to reduce "greenhouse gas pollution, decreasing single-use plastic waste, supporting climate action".
Fans who have bagged tickets should prepare themselves for a shorter show, as Billie previously said that she has no interest in competing with the likes of Taylor Swift, whose performances on her Eras tour last three hours.
"I'm not doing a three-hour show, that's literally psychotic," she told fans earlier this year.
"Nobody wants that. You guys don't want that. I don't want that," she added.
"I don't even want that as a fan. My favourite artist in the world, I'm not trying to hear them for three hours. That's far too long."