Gigi Hadid has a secret singing past that you didn't know about -- find out who she sang backup for!

In "Secrets Uncovered," we delve into the biggest, most forgotten-about secrets in the world of celebrity and Hollywood.

Did you know that Gigi Hadid could sing? We didn't either ... until now.

First, a little background:

The 21-year-old model has been dominating the fashion world for the past couple of years, with her fame skyrocketing her to become the most in-demand model in the world. Along with her younger sister, Bella, and friends like Kendall Jenner and Joan Smalls, Hadid has led a new crop of beautiful young women down the biggest runways in the world.

SEE ALSO: Bella Hadid posts the most adorable throwback photo with big sis Gigi

We first became familiar with Gigi and Bella as background players on Bravo's "Real Housewives of Beverly Hills," as they appeared in numerous scenes with their mother, Yolanda Hadid, herself a former model. During her time on the show, Hadid went by Yolanda Foster, because she was married to Grammy-winning musician, David Foster.

Fast forward to this week when we were scrolling through Twitter and happened upon something very interesting and seemingly unknown about the origins of Gigi's career.

When we first saw this tweet by Music News & Facts, we weren't sure we had read it correctly. It claimed that "Gigi Hadid did the background vocals of multiple songs on Josh Groban's album 'Noël,' which sold over 7M copies WW."

Wait, what?! We, like every other person in this world, follow Gigi's every move through her social media accounts and her time on "Real Housewives," and we had never seen her sing one note of music. Ever.

So we did some digging and, turns out, Music News & Facts was on the money with their tweet.

Back in 2007, Gigi's aforementioned step dad, David Foster, produced the best-selling album of the year which was, you guessed it, Josh Groban's iconic Christmas album, Noël. The album went on to sell over 7 million copies worldwide.

Listen to Josh Groban's iconic Christmas album, Noël, here.

Gigi, then 11 years old, is credited on not one but two songs on Groban's album: "Little Drummer Boy" and "I'll Be Home For Christmas."

On "Little Drummer Boy," you can hear the singing voice of a young girl in the background of the chorus repeating the lines as first sung by Groban. We're guessing that's little Gigi!

On "I'll Be Home For Christmas," her appearance is more blatant: "Hi Daddy! Mommy, Bella and I are wrapping presents to put under the tree, and we saved one especially for you," you can hear her saying over one of the song's interludes. "We miss you a lot, and we hope that you come home soon."

So, we knew that Gigi had ties to the music world through her step dad, but we didn't know until this week that she herself dabbled in singing, most likely at the suggestion of Foster himself.

Further, it looks as though Gigi and Groban interacted a couple of years ago on Twitter, alluding to their little-known collaboration.

There you have it! Gigi Hadid has a secret singing past that you never knew about until now. You're welcome!

See photos of Gigi Hadid through the years:

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