holocaust
c.1250, "sacrifice by fire, burnt offering," from Gk. holokauston, neut. of holokaustos "burned whole," from holos "whole" (see safe (adj.)) + kaustos, verbal adj. of kaiein "to burn." Originally a Bible word for "burnt offerings," given wider sense of "massacre, destruction of a large number of persons" from 1833. The Holocaust "Nazi genocide of European Jews in World War II," first recorded 1957, earlier known in Heb. as Shoah "catastrophe." The word itself was used in Eng. in ref. to Hitler's Jewish policies from 1942, but not as a proper name for them.
Online Etymology Dictionary