'uninterested' originates from the prefix 'un-' meaning 'not' and the word 'interested', which comes from the Latin 'interesse', meaning 'to be between'.

'interesse' transformed into the Old French word 'interesser', and eventually became the modern English word 'interested'. The prefix 'un-' was added to form 'uninterested'.

Initially, it meant 'not having a stake or interest in something', but over time it evolved into its current meaning of 'having no interest or concern'.