2. It can also be used to describe babies... Kin, like the German "chen" is often used to indicate someone or something that is small (or in an endearing mannner), so a little crap is a crapkin. (mostly because babies poop way more than you'd expect) Their diapers can also be called crapkins.
Random mom- "Dangit John, the last thing we need is another crapkin running around here!"
(3)Diaper-changing person- "Eew, little Buddy, you go through crapkins like there's no tomorrow!"