Kein Bock is everyday German slang built around Bock meaning desire or mood in this context, so the phrase signals a complete lack of motivation. Online the extended neeeee version turns that blunt refusal into a meme reaction, shared in chats and short videos whenever work, school, training or a social plan feels like too much. Its appeal is how universal the feeling is, even for listeners who do not speak German the tone alone communicates protest and surrender, which helps it travel as a reusable reaction sound.