Assfoot is what happens when Dad finds you masturbating while peeping through a hole in the downstairs shower, to your mom, sister, cousins, etc., anyone with ass, cunt, and tits.
Derived from the Soul Caliber character "Astaroth" an asstooth is a big, bumbling, klutzy galoomph of a person who is obviously doing something that requires negative use of the brain.
"No, it's probably NOT a good idea to stick your hand in the waffle iron, asstooth"
"whatever ,asstooth" - usually said in exasperation when someone keeps talking about the new plumbing they're installing in their bathroom.