To make someone or something stronger or more brave.
Stoutened can make people think of being brave and strong.
Examples:
The hero's words stoutened the people.
She stoutened her heart and faced the challenge.
The king stoutened his army for the battle.
The knight stoutened himself before the dragon fight.
The magic potion stoutened the little mouse into a big lion.
The coach's speech stoutened the team for the big game.