It's baby-talk: "Popsey" is an affectionate pet name, and "Diddums" is something said to a small child (or sarcastically to an adult) in a kind of mock or playful consolation. "Evvink" is harder to understand. Having skimmed the preceding pages, the only thing I can imagine it means is "Heaven".
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.