A combination of the word Goober, or Snot, which is hailed to be disgusting, and Frak, derived from Fuck, which would entail sexual intercourse.
See also; Gooberfrakker(s), Gooberfraks,
Jock: "Hey there Nerd. I saw you get out of the car with your nerd girlfriend."
Jock: "Well? Were you getting some sweet gooberfrak going on or what?! -laughs and walks away-"