'unimportance' originates from the prefix 'un-' meaning 'not' and the word 'importance', which comes from Latin 'importantia', where 'importare' meant 'to bring in'.

'importance' changed from the Latin word 'importantia' and eventually became the modern English word 'importance'.

Initially, it meant 'to bring in significance', but over time it evolved into its current meaning of 'the state of being significant'.