"And we'll buy you another two presents while we're out today. How's that, popkin?"
- Petunia to Dudley (PS1)
"What about "popkin" and "Dinky Diddydums", can I use them then?"
- Harry to Dudley, on the subject of Dudley's various nicknames (OP1)
Affectionate term used for a small child, from “poppet,” which is a kind of a puppet or doll.