This definition arose from the infamous Youtube between two battle rappers ENJ & NIKS. The guy who got punched in the face proclaimed, before he got dropped "Oh you mad cus im stylin' on you", hence forth it has been a powerful movement.
Some people claim it was first used by Biggie however, in the 21st century, it will always known as this.
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.