According to Whaley, the original linking safety pins was adapted from an old puzzle. Gene Gordon marketed it as “Piff-Paff-Poof” in the early 1930s. It then appeared in print in W. F. Van Zandt's December 1934 Linking Ring column, “Vest Pocket and Impromptu Magic” (Vol. 14 No. 10, p. 841). Dr. E. G. Ervin came up with the idea of shortening the length of the pin bar to facilitate the links. The original gimmicked version of this effect was invented by L. Vosburgh Lyons. See his “Slip, Snap, Spoof: in Phoenix, No. 47, Nov. 5, 1943, p. 192. The gimmick is virtually identical to the construction of Jerry Andrus's pin, released in 1954.
For further information on the evolution of the trick and Linking Pins routines, see Jon Racherbaumer's summery in M-U-M, Vol. 96 No. 5, October 2006, p. 46.