youthfully (part of speech: adverb)
- They are also- and the second emotion springs naturally enough from the first- almost childishly averse from female ugliness. - "The Woman With The Fan", Robert Hichens.
- The negro gazed after her, his month quivering childishly. - "Kildares of Storm", Eleanor Mercein Kelly.
- She remembered them all, and seconds later, when Steve's fingers had closed over her own outstretched hand, she realized that she was staring at him in a childishly concentrated effort to read again in the man's gaze the undisguised worship and wonder which had always followed her from the eyes of the boy who had fought to be her knight. - "Then I'll Come Back to You", Larry Evans.