The state or quality of being strong and thick.
Stoutnesses can be good when talking about physical strength, but it can also mean being a little fat.
Examples:
Her stoutnesses helped her lift the heavy box.
The bear's stoutnesses made it hard to catch.
The tree's stoutnesses made it hard to knock down.
The elephant's stoutnesses made it hard to fit through the door.
The fortress's stoutnesses made it impossible to break through.
The ship's stoutnesses made it impossible to sink.