How Did The Term 'Underdog' Come About?

The origin of the word "underdog" comes from naval shipbuilding when the planks of wood were sawn for their construction. The logs of wood were placed over a pit on planks of wood called "dogs". The senior sawsman stood on top of the plank and he was the overdog (top dog). The junior had to go into the pit and saw and of course he got covered in saw dust. He was the "underdog".