Peter King, in his MMQB, says it came from Philly's quality control coach Press Taylor who saw it used in a 2016 Week 17 game between Chicago and Minnesota.

Link: https://www.si.com/nfl/2018/02/05/super-bowl-52-eagles-patriots-peter-king-mmqb

Excerpt: 

Reich told me the kernel of the idea originated from an industrious Eagles quality-control coach, Press Taylor. Said Reich: “Press has this, what we call this vault of trick plays. It's an immense vault, so every week we go into Press's vault looking for plays.” Taylor, it appears, found the play in a meaningless Week 17 game in 2016. At 1:10 this morning, The MMQB’s Kalyn Kahler found a play from the Chicago-Minnesota game that doubtless led to Target left bunch, Philly special. Bears running back Jeremy Langford took a direct snap from center, quarterback Matt Barkley lined up behind the right tackle, and wideout Cam Meredith circled back behind Langford and took a pitch from him. Barkley leaked out of the backfield into the end zone. No one covered him. At the 11-yard line, Meredith tossed the ball to Barkley, two yards deep in the end zone. Touchdown. Watch that play and keep it in mind. You’ll need it. “We’re fine with ideas coming from anywhere,” Reich said. “Doug loves ideas.”