There is no documented origin for this short nghngh clip, and it is best understood as a generic reaction grunt rather than a line from a known show, film or game. Sounds like this circulate on soundboards because they are short, wordless and easy to recognise, so creators can reuse them without needing context. The spelling follows the sound itself, which helps people find it when they search by imitating the noise. Its popularity comes from that flexibility: the same grunt can suggest effort, embarrassment, frustration or restraint, and it fits into memes, gaming clips and reaction edits.