The story of the bear that the Winnie the Pooh character was named for is in development at RatPac Entertainment.

The company has acquired movie rights to the forthcoming picture book “Finding Winnie,” written by Lindsay Mattick and illustrated by Sophie Blackall.

RatPac Entertainment’s John Cheng and Agustine Calderon will oversee “Finding Winnie” for RatPac.

The book centers on how Lieutenant Harry Colebourn – Mattick’s great-grandfather – bought an orphaned bear cub for $20 in Ontario as he was about to leave for duty in Europe during World War I.

Colebourn nicknamed the cub “Winnie” after his hometown of Winnipeg and took her to Europe, where she became the unofficial mascot of a regiment in England. While Coleburn served in France, he kept Winnie at the London Zoo and eventually donated her to the zoo.

The bear served as inspiration for A.A. Milne’s Winnie-the-Pooh character since his son, Christopher Robin Milne, had named his teddy bear after the bear who he often saw at the zoo.

A 2004 TV movie based on the story, “A Bear Named Winnie,” starred Michael Fassbender as Colebourn.

RatPac Entertainment is a production partnership between Brett Ratner and Australian mogul James Packer. It’s part of the RatPac-Dune Entertainment film finance vehicle formed with Steven Mnuchin and acquired movie rights earlier this month to Harlan Coben’s mystery novel “Missing You” — a day before its publication by Dutton.

“Finding Winnie” will be published in the fall of 2015 by HarperCollins Canada and Little, Brown Books for Young Readers in the U.S.

Jerry Kalajian of Intellectual Property Group arranged the deal in association with Jackie Kaiser of Westwood Creative Artists.