An Etymological Dictionary of the German Language/Kröte
Kröte, f., from the equiv. MidHG. krote, kröte, krëte, f. (even now dial. Krote, Krotte), OHG. chrota, chrëta, f., ‘toad.’ The forms with ë and o are related by gradation; comp. Brett and Bord. The word is peculiar to G.; in OIc. padda, Du. padde, AS. tâdie, E. toad. Etymologically all three are equally obscure.