Get wost and shut up

"Get wost!" I hear Liem say one morning. "Shut up!" he continues. I was shocked to hear this sort of language. I'm sure I've never said anything like that to him. Later on, I hear him again, "Get wost, said the dog to the monkey. Shut up, said the monkey to the dog." Then I realised that he was repeating what he had heard from a book called "The Adventure of Momotaro, The Peach Boy", which we got from some friends in Japan. The offending page is shown as proof! Amazing what he picks up...