'unconcerned' originates from the prefix 'un-' meaning 'not' and the word 'concerned', which comes from the Latin 'concernere', meaning 'to mix together'.

'concernere' transformed into the Old French word 'concerner', and eventually became the modern English word 'concern' through Middle English.

Initially, it meant 'to mix together', but over time it evolved into its current meaning of 'to be involved or worried about something'.