1886, "molecule consisting of several molecules," a sense now obsolete, from macro- + molecule. Apparently coined in "On Macro-molecules, with the Determinations of the Form of Some of Them," by Anglo-Irish physicist G. Johnstone Stoney (1826–1911). Originally of crystals. Meaning "molecule composed of many atoms" is by 1935, from German makromolekul (1922). Related: Macromolecular (by 1931).