The term “holocaust” has its origins in ancient Greek, where it was derived from

The term “holocaust” has its origins in ancient Greek, where it was derived from the words “holos” (whole) and “kaustos” (burnt) to describe a sacrifice completely consumed by fire for a god. It’s used in some translations of the Bible, referring to such sacrifices.

ETYMOLOGY
Holocaust: mid-13c., “sacrifice by fire, burnt offering,” from Old French holocauste (12c.), or directly from Late Latin holocaustum, from Greek holokauston “a thing wholly burnt,” neuter of holokaustos “burned whole,” from holos “whole” (from PIE root *sol- “whole, well-kept”) + kaustos, verbal adjective of kaiein “to burn” (see caustic).

Originally a Bible word for “burnt offerings,” given wider figurative sense of “massacre, destruction of a large number of persons” from 1670s. The Holocaust “Nazi genocide of European Jews in World War II,” first recorded 1957, earlier known in Hebrew as Shoah “catastrophe.” The word itself was used in English in reference to Hitler’s Jewish policies from 1942, but not as a proper name for them.

English chronicler Richard of Devizes in his contemporary account of the coronation of Richard I in 1189 used the word holocaust when he described the mass murder of the Jews of London, although he meant it as “a sacrificial offering.”

EXPLANATION
So, before the World Wars, “holocaust” had general usage to describe any large-scale destruction or slaughter, especially by fire or similar means. It was used to depict vast, catastrophic events such as fires, volcanic eruptions, or other disasters that resulted in extensive loss of life.

The term “holocaust” was also occasionally employed in various historical contexts to refer to mass persecutions and killings, such as the massacre of various groups throughout history.

However, it did not have the specific connotation associated with genocide until the Nazi atrocities against the Jews and other groups became widely known.