This is the 7637th most frequent Japanese word.
勇ん
"勇ん" (いさん) means "to be cheerful, excited, or spirited."
勇んで here means 'boldly' or 'courageously,' describing the manner in which an action is taken.
彼は失敗を恐れずに勇んで挑戦した。
He boldly faced the challenge without fear of failure.
勇んだ implies having an 'enthusiastic' or 'courageous' mood, showing a personal state of determination.
勇んだ気持ちで試合に臨んだ。
He approached the game with a courageous feeling.
勇んで signifies 'with boldness' or 'courage,' characterizing the determined reaction to an external stimulus.