Fook is a variation of fuck. British people prononces fuck as fook. Fookin hell came from fucking hell. It is to show frustration or sometimes to laugh at something ridiculous.
Fookin hell he has a dick on his head.
Fookin hell how did i fail my test?
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.