Origins
The word 'merchandise' entered English in the thirteenth century from Old French 'marchandise' (trade, commerce, goods for sale), a derivative of 'marchand' (merchant), which descended through Vulgar Latin *mercātāns from Latin 'mercārī' (to trade, to buy and sell). The Latin verb derives from 'merx' (goods, wares, commodities), genitive 'mercis,' connected to the PIE root *merk- (to buy, to trade).
Latin 'merx' and its derivatives generated one of the largest commercial word families in English. 'Merchant' (a buyer and seller of goods, from Old French 'marchand'). 'Market' (a place for buying and selling, from Latin 'mercātus,' a place of trade — borrowed into Proto-Germanic as *markatus, giving Old English 'market' and German 'Markt'). 'Commerce' (from Latin 'commercium,' a trading together, from 'com-' + 'merx'). 'Mercantile' (pertaining to trade). 'Mercenary' (one who works for pay — originally a hired soldier, from 'mercēs,' wages). 'Mercury' (Mercurius, the Roman god of trade, thieves, and messengers, named from 'merx' because he presided over commercial exchange).
The most surprising descendant is 'mercy.' Latin 'mercēs' (wages, reward, price) underwent a remarkable semantic shift in Christian Latin. In classical Latin, 'mercēs' was a commercial term: the price paid for goods or services. In the language of the Church, it came to mean 'compassion,' 'pity,' 'the reward of God' — the unearned grace that God extends to sinners. The idea was that mercy is the 'price' that is forgiven, the 'wages' that are not exacted. Old French inherited this Christian meaning as 'merci' (thank you — literally an appeal for mercy or grace), and English borrowed it as 'mercy.' The modern French 'merci' (thank you) preserves the same ecclesiastical shift.
Modern Usage
In modern English, 'merchandise' functions as both noun and verb. As a noun, it means goods available for sale: 'the store's merchandise,' 'branded merchandise,' 'general merchandise.' As a verb, it means to promote the sale of goods: 'to merchandise a product effectively.' The verb sense developed in the twentieth century with the rise of modern retail marketing.
The abbreviation 'merch' (merchandise, especially branded clothing and accessories sold by musicians, sports teams, or media franchises) emerged in the late twentieth century and became standard informal English by the 2010s. 'Band merch,' 'team merch,' 'movie merch' — the word reflects the massive expansion of branded goods as a revenue stream in entertainment industries.
The word's journey from PIE *merk- (to trade) through Latin commercial vocabulary through French feudal terminology to modern retail slang traces the entire history of Western commerce: from ancient markets to Roman trade routes to medieval merchant guilds to modern consumer capitalism. The same root that named the Roman god of trade now names the T-shirts sold at concert venues.