'unexpectedly-improved' originates from the combination of 'unexpectedly' and 'improved', where 'unexpectedly' comes from 'unexpected', meaning 'not anticipated', and 'improved' from 'improve', meaning 'to make better'.

'unexpectedly' evolved from the Old French word 'desesperer', and 'improved' from the Latin word 'improbare', eventually forming the modern English term 'unexpectedly-improved'.

Initially, 'unexpectedly' meant 'not foreseen', and 'improved' meant 'made better', which together evolved to describe something that has become better in an unforeseen manner.