The origin of this short ugh is unclear, but it circulates online as a reaction sound from puffer fish clips, where the fish's puffed cheeks and small mouth make the grunt feel human. Creators use it in short videos and meme edits as a quick way to say no, gross, or not impressed without any words. Its popularity comes from that simplicity: the sound is less than a second long, recognisable, and easy to place over a face, a failed attempt, or an awkward moment. It remains in use because a small, grumpy noise often lands better than a joke.