"Popka" (pronunciation is poo-ka or poop-ka)
You mean "pupka" - Polish term pronounced 'poop-ka'. This is what I've found:
1. pupka - old-fashioned term for a doll - it comes from a German word die Puppe
Nowadays this meaning is not in use and not known for an average Pole.
2. pupka - the term of endearment for a young girl
I've found those above in an online dictionary with the dialect from the area of Poznan, Poland.
Presently in Polish 'pupka' is the diminutive form of a bottom :)