from
Easton's 1897 Bible Dictionary
Augustus
the cognomen of the first Roman emperor, C. Julius Caesar
Octavianus, during whose reign Christ was born (Luke 2:1). His
decree that "all the world should be taxed" was the divinely
ordered occasion of Jesus' being born, according to prophecy
(Micah 5:2), in Bethlehem. This name being simply a title
meaning "majesty" or "venerable," first given to him by the
senate (B.C. 27), was borne by succeeding emperors. Before his
death (A.D. 14) he associated Tiberius with him in the empire
(Luke 3:1), by whom he was succeeded.