From Latin 'merx' (goods) through French 'merci' — originally God's reward for the righteous, now pure compassion.
Compassion or forgiveness shown toward someone whom it is within one's power to punish or harm.
From Old French 'merci' (thanks, mercy, grace, pity), from Latin 'mercēdem' (accusative of 'mercēs,' reward, wages, pay, price), from 'merx' (merchandise, goods, wares). The semantic journey is extraordinary: from 'price paid for goods' to 'reward from God' to 'compassion' to 'thanks.' In Christian Latin, 'mercēs' shifted from 'wages earned' to 'the reward God bestows on the merciful' to 'God's compassion itself.' French
When the French say 'merci' (thank you), they are literally saying 'mercy.' And 'mercy,' 'merchant,' 'commerce,' and 'market' all descend from the same Latin root 'merx' (goods). Mercy began as a business term — the wages God pays the compassionate — before becoming the compassion itself. Gratitude, forgiveness