The word is a synonym for tummy. The specific sort of tummy, that characteristically has more fat (or Schwabbel) than muscel. It doesn't have to be a really really fat tummy. even very thin people lacking muscle can have one
" Oh my god I had so much food, my poor old schwabbelinski will grow evenbigger!"
Pajama casual is a term used when working from home and preparing for a video conference. All business above the waist and your pajama pants down below.