The term Cavalier (//) was first used by Roundheads as a term of abuse for the wealthier Royalist supporters of King Charles I and his son Charles II of England during the English Civil War, the Interregnum, and the Restoration (1642 – c. 1679). It was later adopted by the Royalists themselves. Although it referred originally to political and social attitudes and behavior, of which clothing was a very small part, it has subsequently become strongly identified with the fashionable clothing of the court at the time. Prince Rupert, commander of much of Charles I's cavalry, is often considered to be an archetypal Cavalier.
Cavalier derives from the same Latin root as the French word chevalier (as well as the Spanish word caballero), the Vulgar Latin word caballarius, meaning "horseman". Shakespeare used the word cavaleros to describe an overbearing swashbuckler or swaggering gallant in Henry IV, Part 2, in which Shallow says "I'll drink to Master Bardolph, and to all the cavaleros about London".
"Cavalier" is chiefly associated with the Royalist supporters of King Charles I in his struggle with Parliament in the English Civil War. It first appears as a term of reproach and contempt, applied to the followers of King Charles I in June 1642:
1642 (June 10) Propositions of Parlt. in Clarendon v. (1702) I. 504 Several sorts of malignant Men, who were about the King; some whereof, under the name of Cavaliers, without having respect to the Laws of the Land, or any fear either of God or Man, were ready to commit all manner of Outrage and Violence. 1642 Petition Lords & Com. 17 June in Rushw. Coll. III. (1721) I. 631 That your Majesty..would please to dismiss your extraordinary Guards, and the Cavaliers and others of that Quality, who seem to have little Interest or Affection to the publick Good, their Language and Behaviour speaking nothing but Division and War.
Charles, in the Answer to the Petition 13 June 1642 speaks of Cavaliers as a "word by what mistake soever it seemes much in disfavour". It was soon reappropriated (as a title of honour) by the king's party, who in return applied Roundhead to their opponents, and at the Restoration the court party preserved the name, which survived until the rise of the term Tory.
Cavalier was not understood at the time as primarily a term describing a style of dress, but a whole political and social attitude. However, in modern times the word has become more particularly associated with the court fashions of the period, which included long flowing hair in ringlets, brightly coloured clothing with elaborate trimmings and lace collars and cuffs, and plumed hats. This contrasted with the dress of at least the most extreme Roundhead supporters of Parliament, with their preference for shorter hair and plainer dress, although neither side conformed to the stereotypical images entirely.
Most Parliamentarian generals wore their hair at much the same length as their Royalist counterparts, though Cromwell was something of an exception. The best patrons in the nobility of Charles I's court painter Sir Anthony van Dyck, the archetypal recorder of the Cavalier image, all took the Parliamentary side in the Civil War. Probably the most famous image identified as of a "cavalier", Frans Hals' Laughing Cavalier, shows a gentleman from the strongly Calvinist Dutch town of Haarlem, and is dated 1624. These derogatory terms (for at the time they were so intended) also showed what the typical Parliamentarian thought of the Royalist side – capricious men who cared more for vanity than the nation at large.