youngly

adverb

Etymology: From Middle English yongly, ȝongly, ȝunglich, from Old English ġeonglīċ (“youthful”), equivalent to young + -ly.

Like a young person or thing; young; youthful.
“How youngly he began to serve his country”
“As I mine eye about-e cast, His larg-e beard-e then at last I saw; and thought anon therefore How that his father him before, Which stood upon the sam-e place, Was beardless, with a youngly face.”

Etymology: From young + -ly.

While young; as a youth.
“And that fresh blood which youngly thou bestow'st”
“In six sexless weeks the least "good" of the twenty or so French books I've read is the diary of the youngly-dead Jean-Rene Huguenin (all the rage), because it lacks gossip and carnality, the very stuff of journals.”
In a young or youthful manner; youthfully
“The youngly born brother made no explanation of his sense of offense other than to go over and give Artie a stolid and resounding blow.”
“Refusing to go back to writing things he now thought "youngly glamorous," like Soldiers' Pay, or "trashily smart," like Mosquitoes, he decided to go on even if it meant relinquishing his dream of success.”