Jacqueline Bouvier Kennedy Onassis, a.k.a. Jackie O, is an eternal fashion icon. As First Lady, she became famous for her timeless elegance and chic ensembles.

She made a string of pearls a staple in wardrobes around the world, popularized the Chanel suit and the pillbox hat and was one of the first FLOTUS to ever be photographed wearing pants in candid shots with her children.

Jackie O continues to inspire women decades after her passing in 1994.

During the White House years, she often touted shift dresses and pearls. After, while married to Greek shipping tycoon Aristotle Onassis, it was big sunglasses and big hats with relaxed resort wear.

But one of her most practical pieces of fashion advice is something most people don’t know about. Until now.

A little known secret about Jackie O’s shoes came to light thanks to her former personal assistant, Kathy McKeon.

McKeon arrived as a fresh-faced, eager 19-year-old immigrant from Ireland and earned one of the most envious career opportunities: serving as the personal assistant to Jackie O.

She served as her assistant for more than a decade, from 1964 to 1977, and lived in Jackie’s apartment on Fifth Avenue in New York.

Not too shabby, right?

McKeon learned a slew of secrets from the former first family over the years. While she kept quiet about most of them, she did reveal a few in her new memoir, Jackie’s Girl: My Life with the Kennedy Family.

Kathy McKeon talks "Jackie's Girl: My Life With The Kennedy Family"https://t.co/vZpiml3FpP pic.twitter.com/1Blr1D7DEL — Access (@accessonline) July 5, 2017

McKeon wrote about her life with the Kennedy’s and how she first met them and landed a dream job.

She talked about her relationship with the family as well as small things ordinary people probably wouldn’t know about Jackie.

She gave out a few details of her memoir on an interview with Today.

Watch the video here:

And although she came to the family after the events of November 22, 1963, she also touched on the tragic assassination of John F. Kennedy.

McKeon also spoke about Jackie writing and expressing her concerns about their son, John F. Kennedy Jr. also known as John John, wanting to learn how to fly an airplane. She was insistent on him not flying because she was scared.

Sadly, as most people know, John Jr. died along with his wife and sister-in-law in a plane crash, plummeting into the ocean off the coast of Martha’s Vineyard in July 1999.

Kathy McKeon on how initially fearful Jackie Kennedy was about John F Kennedy Jr learning to fly and his tragic death #latelate pic.twitter.com/GVOXQCbRta — The Late Late Show (@RTELateLateShow) November 24, 2017

She maintained the privacy of the family and the first lady in the memoir – for the most part.

But one of the secrets McKeon did dish on was the fact that Jackie used shoe lifts in most of her shoes.

Almost invisible to the naked eye, these lifts balanced out her legs, as one happened to be a quarter of an inch shorter than the other. You couldn’t tell, but this wasn’t a superficial solution driven by vanity.

Leveling her stride helped to avoid back pain and general discomfort that can come with one leg being shorter than the other, also called leg length discrepancy.

McKeon recalled that the former first lady and style icon’s shoe collection was mesmerizing:

“I had never seen such a dazzling selection of shoes! London-look boots, pumps in every color, spotless sneakers for morning jogs around the reservoir.”

Each shoe had a small lift fastened to the heel.

Shoe lifts aren’t uncommon amongst celebrities, especially men who stand on the shorter side.

Tom Cruise, Simon Cowell, and Robert Downey Jr. add a few inches to their frame with shoe lifts, often concealed and not noticeable unless you point it out…like I did just now.

Sorry about that, guys.

In fact, some suggest Jackie O might have taken inspiration from her husband for the shoe lifts. John F. Kennedy had one leg shorter than the other as well, and opted to wear shoe lifts to aid in his severe back pain due largely to the WWII incident involving PT109.

If you suffer from chronic back pain, shoe lifts may not help, but getting your legs checked couldn’t hurt.

H / T – Southern Living, Fox News, Wiki, Today