Dreadnaught ends of boxcars

I keep hearing the term “dreadnaught ends” for boxcars (and probably gondolas) but have always wondered where did the term come from and what does it really mean. I’ve also seem terms like “3/4 dreadnaught ends”–I assume this is about the number of large corrugations in the end panels. Anyone have info about where the term “dreadnaught” end came from and what it means?

This is from the Merriam Webster on line dictionary. I would think definition three would be the answer:

Main Entry: dread·nought
Pronunciation: 'dred-"not, -"nät
Function: noun
1 : a warm garment of thick cloth; also : the cloth
2 [Dreadnought, British battleship] : BATTLESHIP
3 : one that is among the largest or most powerful of its kind