An Etymological Dictionary of the German Language/Annotated/Donner
Donner, masculine, ‘thunder,’ from the equivalent Middle High German doner, Old High German donar, masculine, corresponding to Anglo-Saxon þunor, English thunder; Gothic *þunara-, masculine. It is the Old Teutonic name for thunder, under which also the weather-god was worshipped (see Donnerstag). The name comes from the Aryan root ten, discussed under dehnen, Dohne, and dünn. In its application to sound we meet with this root in Greek τόνος, ‘string, rope, stretching, tone, accent,’ Sanscrit root tan, ‘to resound, roar, tanayitnú-s, ‘roaring, thundering,’ Latin tonare (Anglo-Saxon þunian, Gothic *þunôn, ‘to thunder’), Latin tonitrus; the latter correspondences are, on account of their meaning, the most closely allied to the Teutonic words.