My guess is 'sacrifice', because isn't that what a holocaust was, in the Old Testament, a sacrifice of an animal on an altar?
I think that in taking away that term is sad. To the Jews (and since my mom was Jewish makes me one too) it wasn't a sacrifice at the extermination camps. My thinking is that the world is trying to put behind itself the murder of all those people, both Jewish, Romani (gypsies) priests, homosexuals, Jehovah Witnesses and all those that the Nazi regime deemed useless peoples.
In the OT a sacrifice to God of an animal was not a Holocaust but a burnt offering to take away the sins of the people (I'm being simplistic here. There's more to it than just that.) The bombing of Dresden was a Holocaust. The atomic bombing of Hiroshima was a Holocaust. The murder of millions of people in the Nazi death camps was a Holocaust.
Sorry for going on like this but I wanted to lay out what really is behind the word "Holocaust"