flail: [OE] Flail is a distant relative of flagellation [15]. Both go back ultimately to Latin flagrum ‘whip’. This had a diminutive form flagellum, which in prehistoric times was borrowed into West Germanic as *flagil-. It is assumed that Old English inherited it as *flegil (although this is not actually recorded), which, reinforced in Middle English times by the related Old French flaiel, produced modern English flail. Flagellation comes from the derived Latin verb flagellāre ‘whip’. => flagellation[flail etymology, flail origin, 英语词源]