There is no single known source for this clip, as a drawn-out aww is a common human reaction rather than a line from a film or show. Short vocal reactions like this became popular on soundboards and in short-form video because they convey emotion instantly without needing context or subtitles. Creators reuse it as shorthand for cuteness, sympathy or playful embarrassment, and its simplicity is why it keeps appearing in reaction edits, compilations and meme videos.