No one in their right mind would put this word into a children's book though, it's absolutely not colloquial. So I suspect sometijng weird going on in the original image.
I've seen long compound words in children's book recently. Could be real.
Some kids get hyper fixated on cool stuff like firefighters, cars, dinosaurs,... and love learning new words in that topic even or especially if they are complicated.
Sometimes those little brains can do a lot more than many give them credit for.
I used to work in a plant with a lot of people from Bosnia. One of them said when she first started working there her English was limited, but she knew the German word for "glove" and asked for some "hand shoes."