'indecipherable' originates from the prefix 'in-' meaning 'not' and the word 'decipher,' which comes from the Old French 'decifrer,' meaning 'to decode.'

'decifrer' transformed into the English word 'decipher,' and with the addition of the prefix 'in-,' it became 'indecipherable.'

Initially, it meant 'not able to decode,' and this meaning has largely remained the same in modern usage.