From Latin 'merx' (goods) via French — same root as 'Mercury,' 'market,' 'mercy,' and 'mercenary.'
A person who buys and sells goods for profit, especially one who trades in bulk or with foreign countries.
From Anglo-French 'marchaunt,' from Vulgar Latin *mercātantem (present participle of *mercātāre, to trade), a frequentative of Latin 'mercārī' (to trade, to buy), from 'merx' (genitive 'mercis,' merchandise, goods). The Latin root 'merx' is of uncertain PIE origin, possibly from *merk- (to seize, to take), suggesting that the earliest concept of trade involved taking or acquiring. The same root produced 'Mercury' (the Roman god of commerce), 'mercy' (originally 'the price paid
The word 'mercy' is an etymological sibling of 'merchant' — both come from Latin 'merx' (goods, merchandise). 'Mercy' evolved from 'mercēdem' (reward, wages, price paid) through Old French 'merci' (thanks, pity) to its modern sense of compassion, making mercy literally 'the price paid' for forgiveness.