“The word Classicus in itself means no more than belonging to a class, but in ancient Rome it was the name of the citizen who belonged to the wealthiest and most heavily taxed class. According to tradition, King Servius Tullius divided the whole Roman population by property into five classes: those in the first class, who paid the highest taxes, were the classici par excellence. Classified apart from them and from proprietors in general were the proletarii, who could not serve the state with their money but only with their offspring; according to Servius Tullius’s division, they constituted the sixth and poorest class.

It is easy to understand that the word classicus was soon transferred to people who excelled above others in other areas. It was used, for example, for a witness who was completely reliable, of a writer of the first rank, of a student who excelled others with his gifts, and so forth.  This distinction continued as long as Latin was spoken, but it disappeared in the Middle Ages [only] to reappear in the time of the Renaissance. The term then assumes the general meaning of excellent and exemplary, and it becomes the designation for whatever is authoritative and serves as a model.  And while humanism assigned authority mainly or exclusively to Greek and Latin writers, classicus became limited to authors of ‘classical’ antiquity.”

Herman Bavinck (1854-1921), “Classical Education”
Essays on Religion, Science and Society
Editor John Bolt
Translators Harry Boonstra and Gerrit Sheeres
(Grand Rapids: Baker Academic, 2008, p. 209)