Diagami occurs when someone has diarrhea and when they excrete their fecal matter. The feces in the toilet is often oddly shaped, distorted or complex which gives it the appearence of origami, hence the words name.
Bill: Sorry man, can't make the movie. I've got one baaad case of diarrhea. It's just flowing through me! It's not all bad though... I created some mad diagami before!
Bob: Sweet mate, what was it?
Bill: One of those birds... A crane I think they're called.