Petir comes from Indonesian and Malay, where it means thunder and lightning, and the extra letters in petirrrrrnih stretch it the way people type a rolling sound online, with nih adding a casual this is it feel. The clip spread through meme soundboards and short video edits in Indonesian speaking communities, then travelled further as a reusable thunder reaction. It stays popular because it works without translation, signalling drama, danger or a joke reveal in a few seconds, and because its exaggerated rumble is instantly recognisable even at low volume.