A shortened version of the words; fucking kill you.
I'll fuckillu you fucking fuck. See also: imgonakillu, illkillyou,etc.
Gawk-off is a phrase used emphatically to get someone to stop gawking at you doing whatever it is you are doing that is drawing their undivided attention. Also used noun gawker, adjective: gawking, etc a lot like the word fuck.
Hey gawk-off you stupid gawker, avert your gaze from my partner and I intensely making out.