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

'illustrāre' 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.'