How the Scottish and Irish spell and pronounce "fuck's sake", or "for fuck's sake".
We don't say that, we just say "fuck sake". Why that would be is anyone's guess, probably just another of our numerous attempts to butcher the English language, which is a fine practice. The likelihood of an entity called "sake" that we are opposed to grows smaller over the years, as far as I can see.
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.