Cavalier and its Romance cognates, Spanish caballero, Portuguese cavalleiro, Italian cavaliere (source of English cavalry ), Old Northern French cavailler, cavaler, Old French and French chevalier (source of English chevalier ), all derive from Late Latin caballārius “horseman, groom,” from Latin caballus “horse, (inferior) horse for riding, packhorse, nag.” In English in the late 16th century, cavalier meant “horseman, armed horseman, knight,” and also “gentleman at arms, courtly gentleman, gallant.”
By the end of the 16th century, cavalier had also become a term of abuse, meaning “braggart, swaggerer,” as in Shakespeare’s Henry IV, Part 2 (1596–99). This sense persisted till at least the English Civil War (1642–1651); the Puritan Roundheads called King Charles’s bellicose aristocratic supporters Cavaliers. By the mid-18th century, a cavalier also came to mean “an attendant upon or escort for a lady, a lady’s dancing partner.”
The adjective senses of cavalier, “offhand, careless, free and easy” arose in the second half of the 16th century; the negative adjective sense “haughty, disdainful” arose in the mid-18th century; the historical sense in reference to the Stuart Royalists arose in the mid-19th century.

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