The story
Blend of dune + doomsday. From the 2026 films Dune: Part Three and Avengers: Doomsday. Coined by analogy with Barbenheimer. Doomsday itself derives from Dr. Doom's + day, and Dr. Doom from doom. Dune derives from dune, as in sand dunes.
Etymology from Wiktionary, CC BY-SA 4.0.