I’m assuming that the second definition was the original definition for ‘Holocaust’ prior to the defeat of NSDAP Germany?
noun: holocaust; plural noun: holocausts
1.destruction or slaughter on a mass scale, esp. caused by fire or nuclear war.“a nuclear holocaust”
the mass murder of Jews under the German Nazi regime during the period 1941–45. More than 6 million European Jews, as well as members of other persecuted groups, such as gypsies and homosexuals, were murdered at concentration camps such as Auschwitz.singular proper noun: Holocaust; noun: the Holocaust
2.historicala Jewish sacrificial offering that is burned completely on an altar.
Middle English: from Old French holocauste, via late Latin from Greek holokauston, from holos ‘whole’ + kaustos ‘burned’ (from kaiein ‘burn’).