1712, "form, shape" (earlier plasm), from Late Latin plasma, from Greek plasma "something molded or created," hence "image, figure; counterfeit, forgery; formed style, affectation," from plassein "to mold," originally "to spread thin," from PIE *plath-yein, from root *pele- (2) "flat, to spread" (see plane, n.1). Sense of "liquid part of blood" is from 1845; that of "ionized gas" is 1928.