'assimilate' originates from Latin, specifically the word 'assimilare', where 'ad-' (appearing as 'as-' before 's') meant 'to, toward' and 'similis' meant 'like'.

'assimilate' changed from the Latin verb 'assimilare' (and the past participle 'assimilatus'), passed through Late Latin and Middle English usage, and eventually became the modern English 'assimilate' (and adjectival/past forms like 'assimilated').

Initially, it meant 'to make similar' or 'to render like', but over time it evolved to include the broader sense 'to absorb or integrate (people, ideas, culture, or substances)' used in modern English.