"breaker or destroyer of images," 1596, from Fr. iconoclaste, from M.L. iconoclastes, from Late Gk. eikonoklastes, from eikon (gen. eikonos) "image" + klastes "breaker," from klas- pt. stem of klan "to break." Originally those in the Eastern Church in 8c. and 9c. whose mobs of followers destroyed icons and other religious objects on the grounds that they were idols. Applied to 16c.-17c. Protestants in Netherlands who vandalized former Catholic churches on similar grounds. Extended sense of "one who attacks orthodox beliefs or institutions" is first attested 1842. Iconoclasm in this sense is from 1858.