With no clear original source, the blabla clip spread as a generic soundboard reaction built around the universal shorthand for empty talk. People have long written blah blah blah for speech that drones on, and this audio version adds laughter to soften the insult into a joke. It circulates in short meme edits, chat audios and prank compilations where a speaker needs to be undercut quickly. Its staying power comes from that simplicity, anyone in any language understands the mock chatter and the giggle that follows it.