"bluster, swagger, be bold, noisy, vaunting, or turbulent," 1580s, from an obsolete noun roister "noisy bully" (1550s, displaced by 19c. by roisterer), from Middle French ruistre "ruffian," from Old French ruiste "boorish, gross, uncouth," from Latin rusticus (see rustic, adj.). Related: Roistered; roistering. Ralph Royster-Doyster is the title and lead character of what is sometimes called the first English comedy (Udall, 1555).