1610s, "of or belonging to the highest class; approved as a model," from French classique (17c.), from Latin classicus "relating to the (highest) classes of the Roman people," hence, "superior," from classis (see class (n.)). Originally in English, "of the first class;" meaning "belonging to or characteristic of standard authors of Greek and Roman antiquity" is attested from 1620s.
"a Greek or Roman writer or work," 1711, from classic (adj.). So, by mid-18c., any work or author in any context held to have a similar quality or relationship; an artist or literary production of the first rank. In classical Latin the noun use of classicus meant "a marine" (miles classicus) from the "military division" sense of classis.