Everything the Greeks had, they got from Kemet(Egypt)*.
The letter "A" is simply an inverted, simplified cow hieroglyph. Some scholars even say it was pronouced "Ah" in ancient Egypt, before becoming "Aleph" in Proto-Sinaitic. Check out this page for more details.
But I like the idea that he just updates his naming and outfit with the times/cultures at hand. I mean, he's not even Apocalypse anymore, he's Revelation.
*who in turn might have descended from Atlantis or some other culture before them.