An Etymological Dictionary of Astronomy and Astrophysics

1. A great or complete devastation or destruction, especially by fire.
   

2. (usually initial capital letter, preceded by the) The systematic mass slaughter of European Jews in Nazi concentration camps during World War II (Dictionary.com).

Etymology (EN): M.E., from L.L. holocaustum, from Gk. holokaustos “burnt whole;” see → holo- “complete, entire, total,” → caustic “burning; burnt.”

Etymology (PE): Harusuc “entirely burnt;” → holo-,
→ caustic “burning; burnt.”