Toby Keith played his last show on December 14, 2023, at Dolby Live at Park MGM in Las Vegas, performing fan favorites like "Red Solo Cup" and "Beer for My Horses."

One song that struck a chord with fans who attended was Keith's hit "Don't Let the Old Man In," which was featured on the soundtrack for Clint Eastwood's 2018 movie "The Mule."

The phrase, which the song was based on, came from a conversation with Eastwood and had a special meaning for Keith, who had asked the actor how he remained so prolific at his age.

"[Eastwood] said, 'I just get up every morning and go out. And I don't let the old man in,'" Keith told Billboard in December 2018. "And I thought, I'm writing that."

Keith became obsessed with it. "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," he told the publication.