I have "heard" that the ".45 Long Colt" name was intended to differentiate the longer ".45 Colt" cartridge from the shorter ".45 Schofield" cartridge that the U.S. Army used in the S&W Schofield revolvers back in the 1870s-1880s. Being shorter, the .45 Schofield cartridge will fit/fire/eject from a revovler chambered for the .45 Colt, but because the .45 Colt has a longer case, the reverse wasn't true.
That's my undrestanding of it too.
