'illustrative' originates from Latin, specifically the word 'illustrativus', where 'illustratus' meant 'enlightened' or 'made clear'.

'illustrativus' transformed into the French word 'illustratif', and eventually became the modern English word 'illustrative' through Middle English.

Initially, it meant 'to make clear or enlighten', but over time it evolved into its current meaning of 'serving as an example or explanation'.