'unfulfilling' originates from the prefix 'un-' meaning 'not' and the word 'fulfilling', which comes from 'fulfill', derived from Old English 'fullfyllan', where 'full' meant 'full' and 'fyllan' meant 'to fill'.

'fulfyllan' transformed into the Middle English word 'fulfille', and eventually became the modern English word 'fulfill'.

Initially, it meant 'to make full or complete', but over time it evolved into its current meaning of 'providing satisfaction or a sense of accomplishment'.