The speaker is referring to their mother's soft, but dirty cotton underwear, warning of a potential leak of poop and the unpleasant scent of MAMA's muffin.
Nasty Mama desires plump, sensitive cunt lips, and you're about to help her destroy her thick, meaty butterfly wings in exchange for a steamy, wet cunt load.
The speaker is discussing their attractive satin underwear and their anticipation for a big cunt underneath, with the promise of a pleasant scent after using cum and cream.