"rough and tough..." comes from the "oscar the pygmy" pun.

It's a particularly LONG pun. Here's the shorthand version:

Oscar (a pygmy, or just a very short, uncivilized, jungle dweller) discovers that there are wonderous things available in America that he just has to get for his people. He sets off on a series of (mis)adventures, thru the Jungle, accross the desert, over a mountain, trying to get onto a ship, then stowing away. Each step along the way, when Oscar seems about to die, he says "I rough, and tough,...."

Finally, cornered on top of the ship's mast, he falls to the deck....SPLAT.

Then, to all the sailors' amazement, he jumps up, unharmed.

How?
He's rough, and tough, and hard to bluff, and used to hard.......ships.