O Fortuna is the opening and closing movement of Carmina Burana, the cantata composed by Carl Orff in 1935 and 1936. Because of its massive choir, pounding rhythm and ominous mood, it became a go-to cue in film trailers, television and parody edits long before short-form memes took over. Online, creators use brief cuts of it to exaggerate suspense, doom or grand importance. Its contrast with everyday footage is exactly why the clip still works so well in modern meme culture.