Eilish initially performed the track, which is titled 'TV', at the AO Arena in Manchester on 7 June, just a few days after a jury awarded Depp millions of dollars in damages for being defamed by Heard.
In the song, she says: "The internet’s gone wild watching movie stars on trial, while they’re overturning Roe v Wade."
The mention of 'Roe v Wade' relates to the landmark US court case which gave millions of women access to abortion – a ruling that was overturned by the US Supreme Court on Friday (24 June).
In an interview with NME released the same day, Eilish explained she had written the song after the Supreme Court's draft opinion on the matter was leaked in May, in the midst of Depp and Heard's highly publicised trial.
The singer said: "I was in this state of depression, losing my own rights to my own body, and then I’d go on the internet and it would be people giving their take on this trial.
"Who f**king gives a f**k? Women are losing rights for their bodies, so why are we talking about celebrities’ divorce trials? Who gives a sh*t? Let them figure it out on their own."
BREAKING: The Supreme Court just overturned Roe v. Wade, ending our constitutional right to abortion. We know you may be feeling a lot of things right now — hurt, anger, confusion. Whatever you feel is OK. We’re here with you — and we’ll never stop fighting for you.— Planned Parenthood (@PPFA) June 24, 2022
Eilish went on to say the internet 'bothers the sh*t' out of her sometimes, and said she and her brother Finneas, who she collaborates with on songs, felt an urge to perform the track while on tour as it reminded them of the early days of Eilish's career.
“I just wanted to go back to my roots: to put a little guitar song back out, and feel like how I used to," she explained. "I was just missing that feeling and missed doing a song that no one had heard yet."
Eilish was performing at Glastonbury the evening that the US Supreme Court effectively overturned Roe v Wade by ruling 6-3 in favour of a Mississippi law that seeks to outlaw abortion at 15 weeks of pregnancy.
While on stage Eilish noted it was a 'really dark day for women in the US', but decided not to comment further because she couldn't 'bear to think about it anymore' at that moment.
A number of other female celebrities have also shared their concerns over the move, with Taylor Swift describing herself as being 'absolutely terrified' that the court had overturned the 50-year-old ruling, while Michelle Obama said she was 'heartbroken'.
Featured Image Credit: BBC/Alamy