The Catholic Encyclopedia says which books are the Catholic Letters but doesn't say how long ago it was that they were called that. I was wondering, because of another post asking for the oldest instance of the term Catholic. Did St. Jerome or Eusebius ever call them that, was it written in the Codex Vaticanus or the Book of Kells or what?
The word Catholic (katholikos from katholou — throughout the whole, i.e., universal) cf. CATHOLIC ENCYCLOPEDIA: Catholic