In Japanese manga and anime, sound effects are written as onomatopoeia, and doon appears whenever something massive lands, explodes, or arrives with intimidating presence. The spelling imitates a low boom that you feel as much as hear. Online, editors borrowed that dramatic convention for memes, edits, and short videos far beyond anime, pairing the sound with zooms, screen shake, and oversized captions. It remains popular because it translates instantly across languages, turning an ordinary clip into a mock-serious moment without needing any explanation or dialogue at all.