Possums are Australian wildlife, and therefore the cuteness is surely only a disguise. They probably have vicious tempers and hidden venomous fangs, and it wouldn't surprise me if they're the larval form of drop-bears.
Meanwhile, according to Wikipedia, the word "possum" is actually derived from "opossum", because of the similarity of the two animals, and "opossum" in turn comes from a Powhatan (native American) word, roughly transliterated as "wapathemwa".