The exact origin of this particular upload is not documented, so its history is best told through the word itself. Uchiwa are the flat, non-folding hand fans of Japan, made from bamboo and paper, and they are closely tied to summer festivals, where dancers and spectators wave them in rhythm with the heat. Because the fans are such a strong seasonal symbol, audio tagged with the word tends to circulate among editors looking for a Japanese summer mood. That cultural shorthand is why the clip keeps getting reused.