The 75-year-old legendary musician said that the two of them put their heads together and came up with the words off a poster in Lennon's room, reported Rolling Stone.
"Well, the great thing is, everyone says, 'John Lennon wrote the lyrics.' ... John and I wrote the lyrics. I went 'round to John's house - and I don't feel like I'm getting paranoid defending my corner, but the actual fact is we sat in his room and said, 'OK, what are we gonna write?'
He added he is glad that he penned the song with the "Imagine" singer.
"That's actually why I do it live. Because, even though John was lead vocalist on it, I like the song and I feel that, having written it with him, and being in the room where it happened, it's a good one to do.
"But yeah we did, we took it right down off this old circus poster we had. So it had Pablo Fanque's Fair and Henry the Horse and the Hendersons, Mr Kite, a 'hogshead of real fire'. All those phrases were directly lifted off the poster," McCartney said.
Disclaimer: No Business Standard Journalist was involved in creation of this content