Little is documented about where Yanyantuuwu first came from, and the clip circulates mainly through user uploaded soundboards under this exact spelling. That kind of naming is common for meme audio, where a sound is reposted, renamed and shared faster than its original source can be tracked. Over time the title itself became the search term, so people look it up by typing the name they saw on a board. It remains in use because it is easy to drop into almost any edit without needing visual context or explanation from the creator.