The Irish singer-songwriter recalled the fling in her new memoir Rememberings.
She said that she wrote the song “Thank You For Hearing Me” (which featured on her album Universal Mother) about her break-up with Gabriel.
“I had had an on-and-off fling with him in which I was basically weekend p***y,” she wrote. “That would be the kindest way to describe it.
“And once I got fed up with being weekend p***y, I wrote this sort of split-up song.”
In the memoir, O’Connor also revealed that she wrote “A Perfect Indian” about the actor Daniel Day-Lewis, claiming “people think we had an affair but we never did”.
“We were getting very friendly until I blew the friendship by losing my temper with him one night in a crazy way that I do sometimes,” she wrote.
“At the time, he was making the movie The Last of the Mohicans, so that’s why it’s called ‘A Perfect Indian’. It’s not that I was in love with him (I wasn’t). But I was very fond of him as a friend.”
Rememberings is published by Sandycove and will be available in hardback from 1 June.