The Beatles singer told a Q&A session with students at the Liverpool Institute of Performing Arts (Lipa) today he had considered a stage name of Paul Ramon in an effort to appear more glamorous.
He joked he might return to it.
The star, who also announced he would play a secret gig somewhere in Liverpool tomorrow, said while the band was on tour with singer Jonny Gentle in Scotland he began introducing himself to girls with the alternative name.
Band mate George Harrison would introduce himself as Carl Harrison and John Lennon would call himself Long John Silver.
Sir Paul said: “We did think we had to be more glamorous.”
He said bandmate Ringo Starr had coined his name while in another group and was always viewed as the “most professional”.
“We weren’t really serious about showbiz, we were just sort of dragged into it,” he said.
“We had to be in it to play.”
The 76-year-old Beatle founded performing arts school Lipa in the derelict Liverpool Institute for Boys, where he had been a pupil, in 1996.
Answering questions in the auditorium, which is named after him, he said returning to the school brought back memories, including getting the cane.
Sir Paul joked: “I’m now heavily into S and M.
“I grew to like it.”
Sir Paul said he and bandmate Harrison, who also attended the school, were “always getting in trouble” and would be given the cane.
He also recounted one incident where Harrison was hit on an artery on his arm with a cane and the following day his father came to the school and punched the teacher who had hit him.
In the Q&A session, which was live streamed on Facebook and hosted by Pulp frontman Jarvis Cocker, Sir Paul revealed he was a fan of Kendrick Lamar and Kanye West’s Dark Twisted Fantasy.
He also said he had been listening to a Christine And The Queens record and added: “It’s like totally a Michael Jackson rip-off, but we don’t mind because it’s so catchy.”
But when asked to name the best musician he had worked with, Sir Paul praised his old bandmates.
He said: “Out of all the ones I’ve worked with it would be the fellow Beatles. It would be John, who was pretty cool, and George and Ringo.
“Having worked with John so one on one I got to see his brilliance before the world did.”
The star said he now listened to music on the radio and through a Spotify account, as well as CDs and vinyl.
He said many albums were now a “collection of singles”, but he had designed new record Egypt Station so it could be listened to in full.
Sir Paul said: “I can’t compete with Taylor Swift, she’s got better legs than me.
“Maybe what I can do is just do what used to be called a concept album, so if you want you can listen all the way.”