Origin: 1885–90; perhaps alteration of Martinez (an earlier alternate name of the drink, of disputed orig.), by back formation (taking it as plural), or by association with the vermouth manufacturer Martini, Sola & Co. (later Martini & Rossi)
1894, probably from Martini and Rossi, It. firm that makes vermouth (an ingredient of the drink). Another theory holds that it is a corruption of Martinez, California, town where the drink was said to have originated.