The classic version of Daumenfrosch appeared on 4chan's /pol/ board on the 27th of March 2018   and on the  board two days later.
More than a year after that the meme was first re-posted in the /deutsch/ (German) general on the /int/ board 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 on /deutsch/ its name is German even though the original creator was American (who never gave it a name however).