'unperturbed' originates from the prefix 'un-' meaning 'not' and the word 'perturbed,' which comes from Latin 'perturbare,' where 'per-' meant 'through' and 'turbare' meant 'to disturb.'

'perturbare' transformed into the Old French word 'perturber,' and eventually became the modern English word 'perturb,' with 'un-' added to form 'unperturbed.'

Initially, 'perturb' meant 'to disturb thoroughly,' and 'unperturbed' has maintained the meaning of 'not disturbed.'