early 12c., "a meeting at a fixed time for buying and selling livestock and provisions," from Old North French market "marketplace, trade, commerce" (Old French marchiet, Modern French marché), from Latin mercatus "trading, buying and selling, trade, market" (source of Italian mercato, Spanish mercado, Dutch markt, German Markt), from past participle of mercari "to trade, deal in, buy," from merx (genitive mercis) "wares, merchandise."
This is from an Italic root *merk-, possibly from Etruscan, referring to various aspects of economics. Meaning "public building or space where markets are held" first attested mid-13c. Sense of "sales, as controlled by supply and demand" is from 1680s. Market value (1690s) first attested in writings of John Locke. Market economy is from 1948; market research is from 1921.