ferule (n.)

"rod or flat piece of wood for punishing children," 1590s, earlier "giant fennel" (early 15c.), from Middle English ferula "fennel plant" (late 14c.), from Latin ferula "reed, whip, rod, staff; fennel plant or stalk" (fennel stalks were used for administering flogging punishment in ancient Roman times) probably related to festuca "stalk, straw, rod."