Apocalypse is the name given to the lead antagonist of this movie.
Having just watched the movie, I believe he was never directly called Apocalypse in-universe. At best, the fate that befell those he ruled are likened to the mythical Apocalypse foretold in religious texts. We know the ancient Egyptians chanted his name, but I didn't catch it.
What is the name he was known by to the ancient Egyptians? Is that his real name as opposed to, say, his many "god names"? If it's not, do we know what it is?