'unprepared' originates from the prefix 'un-' meaning 'not' and the word 'prepared' from Latin 'praeparare', where 'prae-' meant 'before' and 'parare' meant 'make ready'.

'unprepared' changed from the Middle English word 'unpreparid' and eventually became the modern English word 'unprepared'.

Initially, it meant 'not made ready', and this meaning has largely remained the same in modern usage.