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 (Lu 2:1, "Caesar Augustus"), to whom it belonged by adoption, and to Tiberius (Lu 3:1, "Tiberius Caesar"; compare Mt 22:17,21). The "Caesar" to whom Paul appealed (Ac 25:11,12,21) was Nero. The form is perpetuated in "Kaiser" and "Czar."
The International Standard Bible Encyclopedia
Caesar
The International Standard Bible Encyclopedia, James Orr (1915). Public domain, from the CrossWire SWORD module.