You say this term when someone is acting all ghetto to you, and you know that person is shit. It's all talk but no walk, so we say "Achú Misin Qyü" to represent.
Person A - "I am like so totallyhot."
Person B - "Achú Misin Qyü."
Person A - *cries*
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.