"'Christmas Eve' actually wasn't supposed to be a single or a song out for anything," Clarkson, 35, told ABC News. "And then it ended up being such a big song they were like, 'Wait, we want to release this!' And I was like, 'Oh, OK!'"
The song was originally meant to be part of Clarkson's book, "River Rose and the Magical Christmas," she said. But how people received the song surprised her.
"It's literally so fun to sing and it just kind of puts you in this happy mood that gets you ready for Christmas," Clarkson added. "And it's cool because it was like a happy accident. It wasn't supposed to even be, like, a big thing."
In fact, Clarkson likes her song so much that she tweeted Thursday, "Am I jamming to my Christmas album 'Wrapped in Red' and my new song 'Christmas Eve' while finishing up a Christmas present I’m making? Yes. Yes I am!"
After a few non-stop months promoting her new album "Meaning of Life," it's no wonder Clarkson is ready for Christmas festivities.
She said her favorite holiday tradition is one that's not always easy to achieve with her large family: "all being in one place."
"We have a blended family, and we have four kids," Clarkson added, explaining why it's difficult to be under one roof. Still, the singer said when they can gather together, her family focuses on "just celebrating the fact that we're all healthy and happy and blessed."