This sound comes from a user-generated soundboard, where it is tagged simply as a donkey clip, and its exact original recording is not documented. That ambiguity has not stopped it spreading as a meme reaction, because the combination of a stretched human aaaa and a donkey bray is instantly recognisable even without context. Creators tend to reuse it in short-form edits, reaction videos and gaming compilations, where a loud animal noise works as a quick joke in itself. Its staying power comes from that simplicity: one scream, one bray, and an immediate silly payoff.