Just like Zapivon, The Zakuson is a russian term which is often used to describe the things you eat between the shots, or "Things you eat with your Vodka".
It is highly recommended to eat carbonated, dry and small meals such as white bread while you are drinking, for the sake of your stomach.
Nevertheless, it is important to eat something with your drinks anyhow.
"Alex, did you bring any Zakuson?"
"Ma amarti lecha kodem? Daber Ivrit!"
(English translation: Yes, since it's important and healthy.)
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.