'countervail' originates from Middle English, specifically from the combination of Old French 'contre' (from Latin 'contra') and Old French/Old Norman 'valoir' (from Latin 'valere'), where 'contre' meant 'against' and 'valere' meant 'to be strong; to be worth'.

'countervail' changed from Middle English forms such as 'countervailen' (influenced by Anglo-French/Old French), and eventually became the modern English word 'countervail'.

Initially it carried the sense of 'act against in value or worth' (literally to 'oppose in value'), and over time it settled into the general sense 'to offset or counterbalance', which is the current meaning.