'inadequate' originates from Latin, specifically the word 'inadaequatus', where 'in-' meant 'not' and 'adaequatus' comes from 'adaequare' (ad- + 'aequare') meaning 'to make equal'.

'inadequate' changed from the Late Latin word 'inadaequatus' and was reflected in Old/Middle French as 'inadéquat', and eventually became the modern English word 'inadequate'.

Initially, it meant 'not made equal' or 'unequal/not sufficient', but over time it evolved into the current meaning of 'not sufficient; not good enough'.