An adaptation to STFU, which has included a "fucking" to it. Basically translates to "Shut The Fucking Fuck Up!" Has no real purpose except to emphasize that you want the certain someone(s) to shut up.

It’s an acronym standing for Can’t Remember A Fucking Thing. It’s usually used to describe embarrassment at being unable to remember someone (CRAFT moment); going onstage as the lead in the latest theatrical performance and your mind goes completely blank (CRAFT situation); the next morning after a night when you got pissed as a fart and woke up in bed cuddling a traffic cone and a string of fairy lights wound round your prick.

shut the fuckin' fuck up

Shut the flying fuck up.
Similar to stfu but used for more random people.