Meaning

noun a cocktail made of gin (or vodka) with dry vermouth

originMartini is an Italian name, and in the sense of vermouth is used by the Italian company Martini & Rossi. In the sense “cocktail with vermouth and either gin or vodka”, coined in America in the 19th or 20th century, for which various theories exist – perhaps named for the Italian brand of vermouth, perhaps after Martinez, California, perhaps after an Italian bartender of that name.

Etymology from Wiktionary, CC BY-SA 3.0