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). Sense of "pasture, lawn grass" is first recorded 1762. Wyclif (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.
"metal cap on a rod," 1610s, ferule, earlier verrel (early 15c.), from Old French virelle "ferrule, collar" (12c. Modern French virole), from Medieval Latin viriola "bracelet," diminutive of Latin viriae "bracelets," from a Gaulish word akin to Old Irish fiar "bent, crooked," from PIE *wi-ria-, from root *wei- "to turn, twist, bend." Spelling influenced by Latin ferrum "iron."