1560s, from youth + -ful. Old English had geoguðlic. Other words formerly used in the same sense were youthlike, youthly, youthsome, youthy. Related: Youthfulness.
yourn
yours
yourself
youse
youth
youthful
yow
yowl
yowza
yo-yo
ytterbium
)window.location='https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=byronic106@yahoo.com&lc=US&item_name=Donation+to +Help+Keep+Etymonline+Free+and+Open&no_note=0&cn=&curency_code=USD&bn=PP-DonationsBF:btn_donateCC_LG.gif:NonHosted'){kind=link}