Thomas Rhett is opening up about “Mamaw’s House,” his collaboration with Morgan Wallen. The song was a fun write between the two hitmakers, but one neither of them expected to be a single.

“It was the first time we had ever written together,” Rhett reveals on Audacy’s Superstar Power Hour. “The whole song was literally sparked by a phone call that he got in the middle of that write from his grandmother — his Mamaw. Which, if you listen really close, in the beginning of that tune, that’s actual recording of him getting that phone call during our Zoom session. We walked away from that being like, ‘Cool, man. Glad we wrote a song about our grandparents. Moving on.'”

Rhett remembered the song later, when he wanted a new song to include on his 20 Number Ones album, released in September.

“I guess it was like eight or nine months ago, I was like, ‘Do you mind if I put this song out?'” Rhett recalls. “And he was like, ‘Yeah, I love that song.’ And here we are.”

When Rhett and Wallen wrote “Mamaw’s House,” the father of four initially wasn’t sure whose project it would be on, or if it would even be released.

“I think in the beginning, it was like, ‘I wonder if this is going to be on his record. I wonder if this is going to be on mine,'” Rhett says. “And then it wasn’t on either of our records. You write so many songs that at some point, songs just sort of make their way not into the batch. But I think when I was putting together this 20 Number Ones vinyl, I wanted to at least put a new song on there.

“I was going through the catalog, and I had already been working on a new project anyway,” he continues. “I was like, ‘Man, we wrote this song three years ago. This deserves to come out now.’ And so we put it out, and people started playing it. It was really cool.”

Still, although they both liked “Mamaw’s House,” neither Rhett nor Wallen expected the song to do so well at radio.

“I think because we wrote this song so long ago, and when we released it, there was never a plan for it to go on a radio chart of any kind,” Rhett admits. “It was just like, ‘This is cool that we did this together — let’s put it out.’ I think now, to see it organically making its way up the chart is really special.”

When releasing “Mamaw’s House,” Wallen said he wrote it in honor of his beloved grandmother.

“Many times in the past I’ve been open and honest about the love I have for my Mamaw Boots,” Wallen said at the time. “It was only a matter of time before a song was inspired by her. I dedicate this one to not only her but to my living grandmothers as well. I hope they know what a big part they’ve all played in shaping my life. TR had a similar experience growing up so I’m really glad we got to write and record this song together. Hope y’all enjoy it.”

Find “Mamaw’s House” and all of Rhett’s music and upcoming shows at ThomasRhett.com.