The Half Pass originated as a technique to bring cards from the top of the deck around to the bottom, reversed. It appeared in this form in Henri Decremps’s Le Testament de Jérôme Sharp, 1785, p. 161 of the Hugard translation (unpublished), in the context of a Card at Any Number effect. Johann Hofzinser briefly disclosed the modern-day variant of reversing the bottom cards in situ within a letter to friend, Carl von Pospischil on Oct. 27, 1847. This letter can be found in Magic Christian's Non Plus Ultra Vol. 1, 1998, p. 265 of the Pieper translation, with a full description of the technique following in Non Plus Ultra Vol. 2, 2004, p. 36 of the Pieper translation. Six years after Hofzinser's letter, the method hit the printed page in Jean-Nicholas Ponsin's Nouvelle Magie Blanche Devoilee, 1853, p. 49, with no credit to Hofzinser, or anyone else.
This approach didn't seem to catch on with western magicians. Until the early 1930s, the term “Half Pass” was still used to denote the original top-to-bottom technique. The tide began to change c. 1933; see Bob Fisher's trick, “Something With Double Backed Cards,” in The Sphinx, Vol. 32 No. 12, Feb. 1934, p. 372, in which Mr. Fisher defines which of the two Half Passes he is referring to.
Also see Half Pass Covered by a Stripout Action.