Last year, Nicole Kidman shared the key to her marriage, which was then a dozen years strong, with Keith Urban: never texting. A new interview with Urban, however, suggests that there might be more to it than that—and no, it's not that Kidman has repeatedly supported the 51-year-old country singer through his sobriety, or that she's not afraid to join him onstage or in singing duets.

Instead, it's because he knows that she's a "brainiac"—and, well a little bit more than that, as Urban first shared last year on his last album, Graffiti U, which he released in 2018. In a new interview with iNews, Urban took a moment to reflect on the song "Gemini," which just so happens to be his wife's astrological sign. That, he confirmed on Friday, is no accident: "The song is actually about Nicole," he said. And, supportive as she is, it is a bit surprising that, according to Urban, Kidman "loves it." (Though she also apparently loved his controversial song "Female," a simplistic and arguably sexist ode to women that was also on Graffiti U.)

The chorus of "Gemini" doesn't just praise Kidman's intellectual prowess; in fact, Urban may have only done so in the first place to create the rhyme "She's a maniac in the bed / But a brainiac in her head." Those words, Urban continued, were simply "what came out" when his co-songwriter, Julia Michaels, asked him to describe Kidman, presumably inspiring the verse "A little bit left, a little bit right / She's waking to make love in the middle of the night" that follows.

As the Daily Mail points out, the chorus doesn’t end there: The full verse goes, "She's a maniac in the bed / But a brainiac in her head / And I know that everybody knows / Ooh, that she's both." Actually, can’t say we did, Keith!

Related: Nicole Kidman Says She and Keith Urban Have "Never Texted"