'counterfoil' originates from Middle English, specifically the word 'counterfeyt,' where 'counter-' meant 'against' and 'foil' meant 'leaf or sheet.'

'counterfeyt' transformed into the modern English word 'counterfoil' through the influence of Old French 'contrefoil.'

Initially, it meant 'a leaf or sheet against another,' but over time it evolved into its current meaning of 'a part of a document kept as a record.'