'ill-prepared' originates from the combination of 'ill,' meaning 'badly,' and 'prepared,' meaning 'made ready.'

'ill-prepared' evolved from the Middle English use of 'ill' as a prefix to denote something negative or unfavorable, combined with 'prepared,' which has been used since the 14th century to mean 'made ready.'

Initially, it meant 'badly made ready,' and this meaning has largely remained the same in modern usage.