According to Jamy Ian Swiss in Devious Standards, 2011, p. 122, Stuart Gordon executed his technique immediately after dribbling the cards, rather than from a squared deck as the following magicians have since adapted it (although the type of get-ready doesn't affect the turnover itself). The move was reportedly learned from Gordon and used by a select few, such as David Roth and Earl Nelson, as early as 1974, and then published by Larry Jennings and Darwin Ortiz; see The Cardwright by Mike Maxwell, 1988, p. 114, and Cardshark, 1995, p. 106, respectively.
Before that, Ken Simmons published the turnover in Riffling the Pasteboards, 1986, p. 8, but without mention (and seemingly without knowledge) of Stuart Gordon. It was unclear if Simmons intended to claim origination, as he prefaces the trick it appears in, “Ace-Bitiously Yours”, by writing, “You won't find any new or revolutionary moves here…” However, in Banded Deck Effects 1991, Simmons explicitly makes the claim of originality on p. 27. Subsequent research proved that Gordon preceded Simmons; see Wesley James's summary in Enchantments, 2004, p. 164.
The central dynamic of the technique involves the magician sliding his thumb down the face of the double as it's being turned over. This thumb slide is older than Gordon technique. George Pittman utilized it in the Pittman One-Hand Double Lift from The Sphinx, Vol. 48 No. 2, Apr. 1949, p. 35. And in David Ben's Zarrow: A Lifetime of Magic, 2008, p. 341, this thumb slide was used in one of the “Loose Lifts” Zarrow developed c. 1950.