its the stereotypical acoustic shape. smaller an easier to handle so its more popular. very generic yet balanced for large crowds to just playing with friends. its a great shape.
NSW Group FTW!

There's nothing incredibly interesting here.
^^^ Smaller? Smaller than a jumbo perhaps, otherwise dreads are big, full size guitar bodies.
The word itself literally means "fear nothing". They (the guitars) got their name from Martin guitars first one way back because it was bigger than anything else at the time, and decided to name it after the HMS Dreadnought battleship, which was also bigger than any other battleship of that era.