Cocky is also an Australian slang word for "farmer", especially a rich farmer.
For example, one could say "This boarding school is full of nothing but North Shore kids and cockies' sons."
One can speak of a "bush cocky" or a "wheat cocky" or a "pig cocky," in combination with any kind of farming.
This term probably has its roots in yet another Australian word shortening, that of cockatoo to cocky, although the etymology is far from certain, and often debated.