16 This is Jesus Christ who came a High-Priest of the good things to come; who for the bountifulness of His Godhead imparted His own title to us all. For kings among men have their royal style which others may not share: but Jesus Christ being the Son of God gave us the dignity of being called Christians. But some one will say, The name of “Christians” is new, and was not in use aforetime: and new-fashioned phrases are often objected to on the score of strangeness. The prophet made this point safe beforehand, saying, But upon My servants shall a new name be called, which shall be blessed upon the earth. Let us question the Jews: Are you servants of the Lord, or not?
Show then your new name. For you were called Jews and Israelites in the time of Moses, and the other prophets, and after the return from Babylon, and up to the present time: where then is your new name? But we, since we are servants of the Lord, have that new name: new indeed, but the new name, which shall be blessed upon the earth. This name caught the world in its grasp: for Jews are only in a certain region, but Christians reach to the ends of the world: for it is the name of the Only-begotten Son of God that is proclaimed.
Source: Catechetical Lectures (New Advent)