 The shared Proto-Indo-European root is *"tón-r̥" or "*", also found Gaulish "Taranis" and Hittite "Tarhunt".The cause of thunder has been the subject of centuries of speculation and scientific inquiry.Early thinking was that it was made by deities but the ancient Greek philosophers attributed it to natural causes, such as wind striking clouds (Anaximander, Aristotle) and movement of air within clouds (Democritus).