Prior to replacing the late Bon Scott as the lead singer of AC/DC, Brian Johnson met him when Scott's band was opening for Johnson's group Geordie in the early '70s.

In a new interview with the New York Post, Johnson describes how his battle with appendicitis during his gig that night left a lasting impression on Scott.

"I had a terrible case of appendicitis and I went down on my side, kicking and going, 'Ooh!'" remembers Johnson. "But I kept on singing. Apparently, he told the boys when he joined AC/DC, 'I saw this guy Brian Johnson sing, and he was great. He was on the floor, kicking and screaming — what an act!' Of course, it wasn’t an act. I was really ill."

Johnson also speaks about being thrust into the songwriting process for 'Back in Black' immediately after joining AC/DC following Scott's tragic death in 1980.

"They had a very basic riff, and said, 'We were thinking of calling it ‘Shook Me All Night Long'," recalls Johnson. "I sat down that night with this blank piece of paper and within about 15 minutes, I had this song written."

Brian Johnson is promoting a new book called 'Rockers and Rollers: A Full Throttle Memoir.' He recently came under fire by members of the Christian community for blasting religion.

Watch the AC/DC 'You Shook Me All Night Long' Video