According to the Deutsche Welle, “Die Geschichte vom Zappelphilipp” (The Story of Fidgety Philip) was written in 1845 by the German psychiatrist and writer, Heinrich Hoffmann. It’s about a boy who just couldn’t sit still. I think that every German child knows the story.
If someone calls a child a “Zappelphilipp”, whether a girl or a boy, s/he means that it’s a fidgety child.
In English, you’d say to a child, “You’re a fidget. Can you please sit still?”