Recently, Amy has learned that germs can make people ill, and that germs a reason why you should cover your mouth when you cough or sneeze and wash your hands after using the toilet, and that fever is the body's way to "cook" the germs.
She's tried to share this knowledge to others in German, and Stella suggested "Bazillen" as a translation for "germs".
And the other day Stella said that now Amy's talk about "Bazillen" makes her sound rather advanced for her age; I suppose it's a word that children tend not to use much.
I would say that "germs" is a fairly child-appropriate word, so I suppose it's a matter of translation more than of being wise beyond one's years.
Though I'm not sure what a better word is. I suggested "Keime", which seemed similarly generic to me ("Keim" translates "germ" not only in the disease-causing sense but also in the sense of plant seeds—e.g. "Sojakeime/Sojakeimlinge" for "soybean shoots"—and metaphorically for the origin—"to nip in the bud" is "etwas im Keim ersticken", or literally, "to strangle/choke something in the germ").
I also introduced the concept of rhymes to Amy, and we played a game or two of "what rhymes with X".
At one point, she volunteered that "orange" rhymes with "orange", so I presume that the takes the word for the fruit and the word for the colour to be two separate words, which are therefore eligible for consideration (as separate words) in "what word rhymes with what other word". Interesting.