The Origins of Wonder
The double push-off as a technique for a second_deal (see Jean Eugène Robert-Houdin's Les Tricheries des Grecs Devoilées, 1861, p. 169 of the Hoffmann translation) predates its use for a double_lift.
The simulated double push-off often associated with Dai Vernon was created by Laurie Ireland. He published the technique in Ireland's New Card and Coin Manipulation 1935, 1935, p. 9, where it is used in the context of a false count for “Six-card Repeat,” rather than a multiple turnover. Ed Marlo later used the same push-off mechanics for a double lift – both one- and two-handed – in Off the Top, 1945, p. 7. Vernon attempted to claim the same move over twenty years later in Dai Vernon's Ultimate Secrets of Card Magic, 1967, p. 54.