The classic version of Daumenfrosch appeared for the first time on 4chan on the 27th of March 2018.
More than a year after that the meme was first re-posted in the German (Deutsch) general international board section of the same website where it enjoys the most popularity by far and where many variations have originated.
Due to the the character's prevalence there, its name is German even though the original creator was American (who never gave it a name however).