"designation, name given to a person, thing, or class," mid-15c., from Old French apelacion "name, denomination" (12c.), from Latin appellationem (nominative appellatio) "an addressing, accosting; an appeal; a name, title," noun of action from past-participle stem of appellare "address, appeal to, name" (see appeal (v.)).
An appellation is a descriptive and therefore specific term, as Saint Louis; John's appellation was the Baptist; George Washington has the appellation of Father of his Country. A title is an official or honorary appellation, as reverend, bishop, doctor, colonel, duke. [Century Dictionary]