battle:  English acquired battle via Old French bataille and Vulgar Latin *battālia from late Latin battuālia ‘fencing exercises’. This was a derivative of the verb battuere ‘beat’ (source also of English batter and battery), which some have viewed as of Celtic origin, citing Gaulish andabata ‘gladiator’, a possible relative of English bat.
Related words include battalion , ultimately from Italian battaglione, a derivative of battaglia ‘battle’; battlements , from Old French batailler ‘provide with batailles – fortifications or battlements’; and derivatives such as abate, combat, and debate. => abate, bat, battalion, battery, combat, debate
c. 1300, from Old French bataille "battle, single combat," also "inner turmoil, harsh circumstances; army, body of soldiers," from Late Latin battualia "exercise of soldiers and gladiators in fighting and fencing," from Latin battuere "to beat, to strike" (see batter (v.)). Phrase battle royal "fight involving several combatants" is from 1670s.