Strictly speaking, HoloPac is a misnomer - it should be Pepper'sPac.
But even that's not really correct, as the Pepper's Ghost effect was created by Henry Dircks in 1862. Dircks couldn't find a way to sell the idea to theatres, as it was incredibly costly to rebuild performance venues with the necessary technology. John Henry Pepper managed to modify things enough to not require rebuilding, and thus the effect carries his name to this day.
But would the world be as excited about DircksPac?
(If you'd like to learn more about Pepper's Ghost, try Jim Steinmeyer's Hiding the Elephant.)