Carrie Underwood says the last song on her Storyteller album is a "love song for my boys." She's referring to husband Mike Fisher and their almost 8-month-old son Isaiah, of course, but it took some convincing to get her to include "What I Never Knew I Always Wanted" on the album.

"Enough people were like, 'This has to be on the album,'" Underwood tells Taste of Country Nights radio's Sam Alex. Lyrically, the song is more personal than any of the remaining 12 tracks. It may be the most personal song she's ever recorded.

"I finally found / What I never knew I always wanted / I couldn't see / I was blind 'til my eyes were opened / Didn't know there was a hole / Something missing in my soul / 'Til you filled it up / With your love," she sings at the chorus.

“I don’t know if it’s one I’ll perform live often," she says of the final track on an album due Oct. 23. "I have one on ever album. It’s something that’s very deep and personal, it’s just hard in a live setting.”

Becoming a mother didn't change the direction of her fifth studio album. When asked if it has made her a better writer, she says that's not necessarily true, but she does have one more thing to write about.

“I feel like everybody expects this album to be some mushy, hormonal mommy album," Underwood shares.

Storyteller is not that. Already released songs like "Renegade Runaway" and "Heartbeat" show some diversity, while those like "Smoke Break" are more mature songs she probably couldn't have written for albums one through four. "What I Never Knew I Always Wanted" is surely one she couldn't have penned pre-Isaiah. Brett James and Hillary Lindsay helped her write it.

“It’s just one I wrote for me, and Isaiah and Mike," she reveals.

See What (Else) Carrie Underwood Has Been Up to Since Baby