'naysayer' originates from English, specifically the compound of 'nay' + 'sayer', where 'nay' meant 'no' and 'sayer' meant 'one who says'.

'nay' comes from Old English ('nā' / 'nǣ') meaning 'no' or 'not at all', and 'say' from Old English 'secgan' meaning 'to say'. The compound 'naysayer' developed in Modern English (recorded from around the 19th century) as a noun for someone who says 'nay'.

Initially it meant simply 'one who says no'; over time it broadened to refer to habitual opponents or pessimists who routinely reject ideas or predict failure.