'illustrate' originates from Latin, specifically the word 'illustratus,' where 'in-' meant 'into' and 'lustrare' meant 'to make bright.'

'illustratus' transformed into the French word 'illustrer,' and eventually became the modern English word 'illustrate' through Middle English.

Initially, it meant 'to make bright or clear,' but over time it evolved into its current meaning of 'to explain or decorate with pictures.'