'unutterable' originates from Middle English, specifically the word 'unutterable', where 'un-' meant 'not' and 'utterable' meant 'capable of being spoken'.

'unutterable' changed from the Middle English word 'unutterable' and has largely retained its form and meaning in modern English.

Initially, it meant 'not capable of being spoken', but over time it evolved into its current meaning of 'too great to describe in words'.