Why was "tantrum" trending last week?
Old English cniht "boy, youth; servant, attendant," common West Germanic (cf. Old Frisian kniucht, Dutch knecht, Middle High German kneht "boy, youth, lad," German Knecht "servant, bondman, vassal"), of unknown origin. The plural in Middle English sometimes was knighten. Meaning "military follower of a king or other superior" is from c.1100. Began to be used in a specific military sense in Hundred Years War, and gradually rose in importance until it became a rank in the nobility 16c. The chess piece so called from mid-15c. Knight in shining armor in figurative sense is from 1917, from the man who rescues the damsel in distress in romantic dramas (perhaps especially "Lohengrin"). 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.
"to make a knight of (someone)," early 13c., from knight (n.). Related: Knighted; knighting.