It is probably called Crazy Cake because it was so simple to do, and so delicious. Crazy Cake is also very historic, because it was around in World War II when rationing meant it was hard to get stuff for cakes. But some people think this recipe came along in the Great Depression (1929-1941)!
My mother taught me to make it in the 1950's, and the link above is the closest to how I remember her recipe. Don't worry about white vinegar specifically, we always used just plain old apple cider vinegar. Also, this recipe calls for baking soda which I think my mom used, but I read where test kitchens actually say baking powder is even better.
Anyway, chocolate cakes whether scratch or Crazy are SOOOO good, have fun!
A fast way is to use a chocolate cake mix and follow the directions. If you want more chocolate flavor, add a couple of Hershey bars and a package of chocolate instant pudding to the mix and decorate with some shavings. Fast and good.