'inarticulateness' originates from the Latin word 'inarticulatus', where 'in-' meant 'not' and 'articulatus' meant 'distinctly spoken'.

'inarticulatus' transformed into the English word 'inarticulate', and eventually became the modern English word 'inarticulateness'.

Initially, it meant 'not distinctly spoken', but over time it evolved into its current meaning of 'the quality of being unable to express oneself clearly'.