Munya comes from Japanese manga and anime language, where munya munya is the written sound for someone muttering in their sleep. Online, the short clip has spread as a standalone reaction sound on soundboards and in short video edits, separate from any single series. Creators reuse it because the sleepy mumble is understood without translation and fits anime edits, VTuber clips and cute animal videos alike. Its brevity and soft tone keep it popular for marking drowsiness rather than a dramatic punchline.