'interest' originates from Latin, specifically the word 'interesse,' where 'inter-' meant 'between' and 'esse' meant 'to be.'

'interesse' transformed into the Old French word 'interest,' and eventually became the modern English word 'interest' through Middle English.

Initially, it meant 'to be of importance,' but over time it evolved into its current meanings of 'curiosity' and 'financial return.'