In the phrase "render unto Caesar . . . " the word Caesar (referring to the
current emperor Tiberius but also generic, I think, pretty much a synonym for
"emperor") has become almost a title,not a name--although Tiberius did have
it as part of his full name, too: Tiberius Julius Caesar Augustus. Both
"Caesar" and "Augustus" are acquiring this generic status already in the 30's
Hope this helps.