The final No.1 of Toby Keith‘s successful career seems a fitting bookend for one of country music’s biggest stars. The Oklahoma native had an unexpected, muiti-week No. 1 hit with “Don’t Let the Old Man In,” a song he originally wrote and recorded in 2018.

Keith performed the song live at the inaugural 2023 People’s Choice Country Awards, where he was presented with the People’s Country Icon Award, given to him by Blake Shelton. The song was originally written by Keith, after he was inspired by a conversation he had with Clint Eastwood.

Both Keith and Eastwood were golfing together at a tournament, and Eastwood told Keith he was soon going to start shooting a movie, The Mule, with the first day of filming happening to be Eastwood’s 88th birthday. Intrigued, Keith asked Eastwood how he kept working when he was already well into his 80s.

He said, ‘I just get up every morning and go out. And I don’t let the old man in,’ ” Keith recounted to Billboard. “And I thought, ‘I’m writing that.’”

Once Keith had the idea, he became consumed with making “Don’t Let the Old Man In,” the best it could be.

“People were talking to me and they would say, ‘Did you hear what I just said?’ And I was like, ‘No,’ because I wasn’t listening to any conversations. I was consumed by ‘Don’t Let the Old Man In.’ I worked so hard on it,” Keith recalled. “When I finally sang the line, I thought, it’s got to be dark, it’s got to be a ballad and it’s got to be simple.”

Keith didn’t write “Don’t Let the Old Man In” to be part of The Mule, but as soon as Eastwood heard it, he knew he wanted it in the film.

“He said, ‘I’ve got a spot in the movie and I’m putting it in there,’” Keith remembered Eastwood telling him. “And then Warner Bros. called asking did I read the script before I wrote this song because it fits perfectly.”

After Keith’s performance, Lady A‘s Charles Kelley shared how he had a unique connection to the reflective tune.

“I’m 90 percent sure I was with you the day that you came up with that song idea. We were playing in The Clint,” Kelley recalled to Keith, referring to the golf tournament that they both participated in together. “You were playing with Clint Eastwood, and I was playing with his buddy, Steve John … I believe that you asked Clint, ‘What’s the key? What’s the key to just growing old?’ and he had said, ‘Don’t let the old man in.’

“I can’t remember if you wrote it down,” Kelley continued. “You obviously must have held onto it. It’s just crazy to think that it’s now the No. 1, most-added. It looks like it’s about to be a hugely impactful song. It’s pretty cool to be a fly on the wall during that moment. That’s what great songwriters do.”

Keith passed away on February 5, after being diagnosed with  stomach cancer in 2021. His performance at the People’s Choice Country Awards was his last live televised performance. Keith previously said he planned to tour in 2024. Funeral services have yet to be announced.