User blog comment:AmaLlama16/What does Niyo mean/@comment-24208349-20140704024440

Yeah, Prussia has a line like that in his character song and in Episode 24. Actually, "niyo niyo" is Japanese onomatopoeia for "smirk" or "sneer". Himaruya uses that a lot, but most people call it "niya niya". Considering England and his tsundere personality, "niyo niyo" seems to fit him!