1650s, "of the nature of a literary romance," from French romantique, from Middle French romant "a romance," oblique case of Old French romanz "verse narrative" (see romance (n.)).
As a literary style, opposed to classical since before 1812; in music, from 1885. Meaning "characteristic of an ideal love affair" (such as usually formed the subject of literary romances) is from 1660s. Meaning "having a love affair as a theme" is from 1960. Related: Romantical (1670s); romantically. Compare romanticism.