Battalion comes from Italian 'battaglione' (a large battle group), an augmentative of 'battaglia' (battle), from Latin 'battuere' (to beat).
A large body of troops ready for battle, especially an infantry unit forming part of a brigade; a large organized group of people pursuing a common aim.
From French 'bataillon,' from Italian 'battaglione' (a large group assembled for battle), augmentative of 'battaglia' (battle), from Late Latin 'battālia' (fighting exercises, combat), from Latin 'battuere' (to beat, to strike). The augmentative suffix '-one' indicates a large version of the base — a battalion is literally 'a big battle group.' The word entered English during the military revolution of the 16th century when European armies were being reorganized. Key
The word 'battery' comes from the same Latin root 'battuere' (to beat). A battery of artillery was a group of guns beating the enemy. When Volta invented his electric pile in 1800, Benjamin Franklin had already used 'battery' for a group of connected Leyden jars — and the name stuck for all electrochemical cells.