ferule n.

1510s, "teacher's pointer," alteration of festu "piece of straw, twig" (late 14c.), from Old French festu "straw; object of little value" (12c., Modern French fétu), from Vulgar Latin *festucum, from Latin festuca "straw, stalk, rod," probably related to ferula "reed, whip, rod" (see ferule). The sense of "pasture, lawn grass" is attested from 1762. Wycliffe (1382) has festu in Matthew vii.3 for the "mote" in the eye. In Old French rompre le festu was to symbolically break a straw to signify the breaking of a bond.