'doom-monger' is a modern English compound formed from 'doom' + 'monger', where 'doom' means 'judgment, fate, or ruin' and 'monger' is used figuratively as 'one who spreads or promotes' rather than literally a seller.

'doom' comes from Old English 'dōm' meaning 'judgment, law, fate' (from Proto-Germanic *domaz). 'monger' descends from Old English 'mangere' meaning 'trader' or 'seller'; in Modern English the element '-monger' became productive in figurative compounds (e.g., 'scaremonger', 'warmonger'), leading to formations like 'doom-monger' in more recent usage.

Originally 'monger' meant 'seller' or 'merchant'; over time it acquired a figurative sense 'one who deals in or spreads' something (often undesirable). Thus 'doom-monger' evolved to mean 'one who spreads doom' rather than a literal seller of doom.