Woody is the cowboy sheriff from Pixar's Toy Story, first seen in the 1995 film, and the character has appeared across sequels, shorts and many licensed games since then. This short hello comes from a game version of the character rather than a film scene, which is why it is so clean and isolated. Single word greetings like this travel well on soundboards and in edits, because they need no context to understand. Creators keep reusing it as a quick, recognisable way to say hello without recording their own voice.