'unmistakable' originates from the prefix 'un-' meaning 'not' and the word 'mistake,' which comes from Old Norse 'mistaka,' meaning 'to take in error.'

'mistake' evolved from the Old Norse word 'mistaka' and eventually became the modern English word 'mistake.' The prefix 'un-' was added to form 'unmistakable.'

Initially, 'mistake' meant 'to take in error,' and 'unmistakable' has always meant 'not able to be mistaken.'