While the idea of secretly buckling the bottom card of a deck or packet did not start appearing in published works until 1940, the technique was known and used centuries earlier, as has been discovered in an unpublished, anonymous book on conjuring cataloged as “MSS III, 18” in the Biblioteca di Asti, Italy, dated c. 1670-1730. An English translation of much of this work was made by Lori Pieper in the Winter 2013 issue of Gibecière (Vol. 8 No. 1). On page 105 of this translation are two approaches to buckling the bottom card in the context of doing a form of the Glide. In both versions, the second fingertip presses near the outer right corner to buckle the bottom card, in the first case diagonally, in the second case sidewise.
Early published descriptions of the Buckle taught using all four fingers or the third or fourth fingers at the side of the deck or packet to accomplish the Buckle of the bottom card. Edward Marlo was the first to publish the idea of using of the first finger at the outer right corner for doing the Buckle, in which the card was buckled sidewise, down its length (see his Deck Deception, 1942, p. 21). He could not have known that in “MSS III, 18” (above), the anonymous author described a very similar approach, using the second finger. When Dai Vernon included a description of using the forefinger to buckle the bottom card diagonally, in his “Mental Card Miracle” (Stars of Magic, Series 5 No. 3, 1949), for taking the card into Gambler's Cop, Marlo extended the idea to the Double Buckle and Triple Buckle. See his The Cardician, 1953, p. 102. However, Herb Zarrow also claimed to have come up with the same Double Buckle technique. Given the age of the Buckle and the popularity of the Buckle Count, independent invention was, perhaps, inevitable. However, in the case of Marlo and Zarrow, things were contentious. Zarrow claimed to have shown Marlo the Double Buckle more than a year before The Cardician was published. Long an underground debate, Zarrow's side of the story was eventually aired by David Ben in Zarrow (2008, p. 62). For more in defense of Marlo on the issue, see Jon Racherbaumer's essay, “What about the Buckle Count?”, in the April 1992 issue of The Olram File (Vol. 1 No. 11, unpaginated).
Also see Buckle Count.