Swift said in a new interview with ABC News that she was inspired by the journey of Jessie, the beloved cowgirl ragdoll in the animated movie franchise.
"We have seen her go through such heartbreak and such, you know, triumphs and loss and we learned her back story," Swift said in an interview that aired Wednesday on "Good Morning America." "But in 'Toy Story 5' we see such a character development and, really, lessons that I could relate to as she's grown up and as she has learned more about her experiences and her memories."
The singer continued, "Just the feeling that, like, sometimes people's paths diverge, and that doesn't mean that that's the last time that you get to feel those memories or know that person."
When the song was released on June 5, Swift revealed that she collaborated on it with singer-songwriter and producer Jack Antonoff. She shared on social media that they wrote the song with "adoration" for the "Toy Story" characters that were staples of their childhoods.
"All you said was, 'Hi' / And I remembered I loved you / Came back when it mattered, I saw you / Standing there in the light of the window / wearing that same smile," Swift sings on the track.
Swift performed "I Knew It, I Knew You," for the first time live at the "Toy Story 5" world premiere Tuesday night in Los Angeles.
The "Shake It Off" singer also performed "You've Got a Friend in Me" alongside Randy Newman, the song's singer-songwriter and the man behind some of the most classic songs from the "Toy Story" franchise.
"Toy Story 5," a Disney and Pixar film, is scheduled to premiere in theaters on Friday, June 19.
The movie features the iconic toys Woody (Tom Hanks), Buzz Lightyear (Tim Allen) and Jessie (Joan Cusack) coming face-to-face with new nemesis Lilypad (Greta Lee), a frog-shaped tablet.
Swift posed at the film's premiere with its stars, including Cusack, who voices Jessie on the big screen.
The singer also brought a collectible, her original VHS copy of "Toy Story," for the movie's stars to sign.
Swift told ABC News that as a longtime "Toy Story" fan herself, it was a "poignant" moment for her to pen and perform a song for the movie's latest release.
"I watched 'Toy Story' when I was 5 and I've watched every single one of the films so many times," she said. "So I really think that like, to be able to be welcomed into something that has welcomed me, unknowingly, its entire existence, just as a fan, feels like very poignant for me and for my family."
The Walt Disney Co. is the parent company of Pixar and this station.