Caesar in the Bible Encyclopedia - ISBE

se'-zar (Kaisar): Originally the surname of the Julian gens (thus, Caius Julius Caesar); afterward a name borne by the Roman emperors. In the New Testament the name is definitely applied to Augustus (Lk 2:1, "Caesar Augustus"), to whom it belonged by adoption, and to Tiberius (Lk 3:1, "Tiberius Caesar"; compare Mt 22:17,21). The "Caesar" to whom Paul appealed (Acts 25:11,12,21) was Nero. The form is perpetuated in "Kaiser" and "Czar."