Giaour
Adjective that I have no idea how to pronounce
One outside of the Islamic faith; infidel
Since he was born well before Mohammed, Nero was definitely a giaour.
This one harkens back to 1564, and does not come from Latin. In fact it comes from French, who got it from Italian word giaur, who took it from the Turkish word gâvur, who cribbed it from the Persian gawr, or gabr.