Corned beef comes from the brisket and silverside (just under the topside) of the cow. Both of these are tough cuts requiring either long, slow cooking, or pickling in brine, or both - hence their...
This is the heart of any cut of beef against the grain. If it was a pave of rump, it would be the middle / best / heart of the meat / rump, cut against the grain.
Corned beef is derived from cattle (beef), not from pigs (pork). Also, don't mistake 'corned beef' for 'corn-fed beef'. 'Corned beef' is a brine cured cut of beef, whereas 'corn-fed beef' is cattle...