'unpromising' originates from the prefix 'un-' meaning 'not' and the word 'promising', which comes from the Latin 'promittere', where 'pro-' meant 'forward' and 'mittere' meant 'to send'.

'promittere' transformed into the Old French word 'promettre', and eventually became the modern English word 'promise', with 'un-' added to form 'unpromising'.

Initially, 'promittere' meant 'to send forward', but over time it evolved into its current meaning of 'not likely to succeed'.