Kitto's Popular Cyclopedia of Biblial Literature
Cæ´sar, a name assumed by, or conferred upon, all the Roman emperors after Julius Caesar. In this way it became a sort of title like Pharaoh, and, as such, is usually applied to the emperors in the New Testament, without their distinctive proper names (Augustus). The Caesars mentioned in the New Testament are Augustus (); Tiberius (; ). Claudius (); Nero (); Caligula, who succeeded Tiberius, is not mentioned.
Kitto, John, ed. Entry for 'Caesar'. "Kitto's Popular Cyclopedia of Biblial Literature". https://www.studylight.org/encyclopedias/eng/kbe/c/caesar.html.