'conscientiousness' originates from the Latin word 'conscientia,' where 'con-' meant 'with' and 'scientia' meant 'knowledge.'

'conscientia' transformed into the Old French word 'conscience,' and eventually became the modern English word 'conscientiousness' through Middle English.

Initially, it meant 'knowledge within oneself,' but over time it evolved into its current meaning of 'diligence and carefulness in one's duties.'