This expression refers to removing the very tough skin from the delicate flesh of a catfish.
There are many ways to skin a catfish and all were initially developed through
trial and error in attempt to find the best way to remove the skin without tearing
the edible flesh into smaller bits and chunks. Like most fish, an intact one-piece
half-fish fillet of catfish is most desirable for cooking (battered, breaded, and
pan fried). To obtain such catfish fillets, takes knack and technique.