Old English cniht "boy, youth; servant, attendant," a word common to the nearby Germanic languages (Old Frisian kniucht, Dutch knecht, Middle High German kneht "boy, youth, lad," German Knecht "servant, bondman, vassal"), of unknown origin. For pronunciation, see kn-. The plural in Middle English sometimes was knighten.
Meaning "military follower of a king or other superior" is from c. 1100. It began to be used in a specific military sense in the Hundred Years War, and gradually rose in importance until it became a rank in the nobility from 16c. Hence in modern British use, a social privilege or honorary dignity conferred by a sovereign as a reward, without regard for birth or deeds at arms. In 17c.-19c. a common jocularism was to call a craftsman or tradesman a knight of the and name some object associated with his work; e.g. knight of the brush for "painter." Knight in shining armor in the figurative sense is from 1917, from the man who rescues the damsel in distress in romantic dramas (perhaps especially "Lohengrin"). For knight-errant, see errant.
The horse-headed chess piece so called from mid-15c. Knights of Columbus, society of Catholic men, founded 1882 in New Haven, Connecticut, U.S.; Knights of Labor, trade union association, founded in Philadelphia, 1869; Knights of Pythias, secret order, founded in Washington, 1864.
late 14c. (c. 1200 as a surname), "mounted knight, armed horseman of noble birth," from Anglo-French chivaler "mounted knight," Old French chevalier "knight, horseman, knight in chess" (12c., Modern French chevaler), from Late Latin caballarius "horseman" (source of Provençal cavallier, Spanish caballero, Portuguese cavalleiro, Italian cavaliere; see cavalier (n.)). The word was nativized in Middle English ("chevaleer"), but has been given a French pronunciation since 16c.
"give a name to," originally "make a knight," from late Old English dubbian "knight by ceremonially striking with a sword" (11c.), a word perhaps borrowed from Old French aduber "equip with arms, adorn" (11c.) which is of uncertain origin, probably Germanic, but there are phonetic difficulties. Meaning "provided with a name" is from 1590s. Related: Dubbed; dubbing.