'demonstrability' originates from Modern English, specifically the word 'demonstrable' combined with the suffix '-ity' (from Latin '-itas'), where 'demonstrable' ultimately comes from Latin 'demonstrare', in which 'de-' meant 'completely' and 'monstrare' meant 'to show'.

'demonstrability' changed from Latin 'demonstrare' to Old French 'demonstrer', then into Middle English forms related to 'demonstraten'/'demonstrate' and the adjective 'demonstrable', and eventually became the modern English noun 'demonstrability' through the addition of the suffix '-ity'.

Initially, it meant 'to show or point out', but over time it evolved into its current meaning of 'the quality of being able to be shown or proved'.