Joe Alwyn's pseudonym on his girlfriend Taylor Swift's albums was named after his great-grandfather.
The 'Conversations With Friends' star has two co-writing tracks on his significant other's 'Folklore' record and three on her follow-up album 'Evermore' under the pseudonym William Bowery, and he chose the moniker because of his composer relative and that he's a big fan of the New York area Bowery.
He said: "It was a combination of William, my great-grandfather - who I actually never met - [who] was a composer.
"He wrote a lot of classical music and he wrote a lot of film scores. And then Bowery is the area in New York that I spent a lot of time in when I first went over there. So, stick 'em together."
Joe joked the name he chose is "very fancy" and could easily be confused for a character in the detective novels of legendary writer Dame Agatha Christie.
Speaking on 'The Kelly Clarkson Show', he added: "We chose to do it so the people, first and foremost, would listen to the music first before dissecting the fact that we did it together.
"We did it under the name William Bowery, very fancy. It sounds like a kind of Agatha Christie character that should be wearing a monocle with a big moustache."
Earlier this month, the 31-year-old actor admitted his collaborations with 32-year-old Taylor were "accidental".
He said: “It was really the most accidental thing to happen in lockdown.
"It wasn’t like, ‘It’s three o’clock, it’s time to write a song!’ It was just messing around on a piano and singing badly and being overheard and then thinking, you know, 'What if we tried to get to the end of it together?' "
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