1867, originally endosmose (1830s) "inward passage of a fluid through a porous septum," from Fr. endo- "inward" + Gk. osmos "a thrusting, a pushing," from othein "to push, to thrust," from PIE *wedhe- "to push, strike" (cf. Skt. vadhati "pushes, strikes, destroys," Avestan vadaya- "to repulse"). Fig. sense is from 1900.