E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The best authors. The Romans were divided by Servius into six classes. Any citizen who belonged to the highest class was called classicus, all the rest were said to be infra classem. From this the best authors were termed classici auctorës (classic authors), i.e. authors of the best or first class. The high esteem in which Greek and Latin were held at the revival of letters obtained for these authors the name of classic, emphatically; and when other first-rate works are intended some distinctive name is added, as the English, French, Spanish, etc., classics.