The 27 year-old made the admission on evertonfc.com, having coming through the German club's youth system.
"It was my biggest dream to play for Eintracht. I dreamed of it every day," Tosun said.
"I was in Frankfurt at the wrong time. We had a lot of good strikers, so it was hard to get games."
He would eventually move to Gaziantepspor to make a senior breakthrough.
"I was initially frustrated with this decision, but in the end it was the right one."