I wondered for a long time why you wrote about ass and realised it when I found out chubby also means plump.
So, there is a misunderstanding on your part because pucołowaty doesn`t refer to the whole body being plump but only to cheeks.
Pucołowaty - chubby cheeked. Hence pućka - a female with chubby cheeks.
maybe 'pucki'? fat cheeks...
I tried to image- google pućka and all images show pets like cats, dogs or even owls. It has stopped bearing that human connotation in Polish.