I felt the "tush-push" was just a "pussified" version of the Flying Wedge.
My grandfather played halfback at Vanderbilt in the mid-to-late 1890's.
He wore a special "brace" under his special jersey. The brace had two handles that protruded through two slots in his jersey. The back field had two players, each of whom would grab a handle and in one joint movement, throw my grandfather over the line of scrimmage.
Now that I see what I have written, maybe the "Flying Wedge" was the forerunner of the forward pass? - LOL