The phrase comes from everyday Brazilian Portuguese slang, where burro leso combines two insults for someone slow or foolish, and do carai adds crude emphasis. Short shouted insults like this spread widely as WhatsApp audios and soundboard clips in Brazil, passed between friends as instant reactions rather than tied to a single show or creator. Its popularity comes from how specific and rhythmic the wording sounds, making it instantly recognisable even out of context and easy to reuse across memes, edits, and chat replies.