Well, I'm guessing that his photo of the NS unit, and notation of "Catfish", is a humorous poke at the vague resemblence of that style engine to a catfish. Boxcab E50
The reason for the nickname is the action stripes look like cat whiskers on the nose of the wide-body cab and the rear radiator flares look like the tail. Of course the thing that tops it all off is when the cab door on the front is open for some natural A/C and it looks like it is meowing.
Now those are some good eatin' there OLDRK. Would be fun to fry one of those up while watching the other kind of catfish glide by on the rails. You have to admit that it is a good nickname for those NS Dash 9's.