Baconburn is a rash specifically on the inner thighs of a fat person from walking. The thighs are so fat, they rub up against each other when the person is walking, and causes burning, chaffing and redness, similar to the sight of bacon.
Oh man, that chick is so fat, her thighs are walking around each other; she must get bad bacon burn. Or:
Yo, that fat chick is burning some bacon, you see that?
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.