'unclassifiable' originates from the prefix 'un-' meaning 'not' and the word 'classifiable' which comes from 'classify', derived from the Latin 'classificare', where 'classis' meant 'class' and 'facere' meant 'to make'.

'classificare' transformed into the French word 'classifier', and eventually became the modern English word 'classify', leading to 'classifiable' and then 'unclassifiable'.

Initially, it meant 'not able to be placed into a class or category', and this meaning has largely remained the same in modern usage.