Shamrock Shakes, the minty treat from McDonald's that is available annually around St. Patrick's Day, actually have a huge charitable element thanks to an idea from the Philadelphia Eagles.

The Shamrock Shake® was created in 1967 by Hal Rosen, a Connecticut McDonald’s Owner and Operator who made the mint shake in celebration of St. Patrick’s Day. Three years later, Shamrock Shakes debuted nationally and became an instant success across the country.

However, as the Atlanta branch of Ronald McDonald House Charities explains, Shamrock Shakes have another legacy that even its most loyal fans may not know.

When Philadelphia Eagles tight end Fred Hill's three-year-old daughter Kim was being treated for leukemia in 1974, his life changed.

He and his wife Fran camped out on hospital benches and sat in cramped waiting rooms during Kim's three years of treatment. The Hills watched other parents and families of seriously ill children do the same thing. Many of the families had to travel long distances for their children to receive medical treatment and couldn't afford hotel rooms.

The Hills knew there had to be a solution. Hill rallied the support of his Eagles teammates to raise funds. Through Jim Murray, the Eagles' general manager, the team offered its support to Dr. Audrey Evans, head of the pediatric oncology unit at Children's Hospital of Philadelphia. Dr. Evans had long dreamed of a 'home away from home' for families of children being treated at her hospital.

Murray called Don Tuckerman, a friend from the local McDonald's advertising agency.

"What's your next promotion?" Murray asked.

"St Patrick's Day," Tuckerman said. "Shamrock Shakes."

It was perfect: The milkshakes were green—the Eagles' color!

According to a 2017 essay published by the Philadelphia Eagles, Murray then asked if McDonald’s would be willing to donate 25 cents of each Shamrock Shake to help pay for the house, and Tuckerman put him in contact with the company’s regional manager, Ed Rensi.

Rensi’s answer was simple: “What if we give you all the money? Can we call it the Ronald McDonald House?"

Murray said: "If you give us all the money, you can call it anything you want to."

The very first Ronald McDonald House was purchased on Spruce Street in Philadelphia for $42,000, funds raised by the Shamrock Shake sales. It officially opened on October 15, 1974.

“The Philadelphia Eagles started everything, and now there are 365 houses in 63 countries on six continents," Hill said in 2017.

“It’s unbelievable because they’re needed so badly. They’re all over the world, and it all started in Philadelphia.”

Ultimately, Kim Hill lived to be 40 years old, far exceeding the six months that her doctors had given her when she was first diagnosed as a toddler.

“Kim said, ‘I didn’t like being sick, but in a way, I’m kind of glad I did get sick because through all my suffering, a great thing has come from it,’” Hill said.

Today, the Eagles and the Philadelphia Ronald McDonald House still work hand in hand through the Eagles Care partner program.

Meanwhile, McDonald's announced this month that the iconic Shamrock Shake® (and OREO® Shamrock McFlurry®) are making their return to participating restaurants nationwide starting February 5, for a limited time.