young

young young folks think old folks to be fools, but old folks know young folks to be fools proverbial saying, late 16th century, asserting the value of the experience of life which comes with age over youth and inexperience.
a young man married is a young man marred proverbial saying, late 16th century, often used as an argument against marrying too young.
young men may die, but old men must die proverbial saying, mid 16th century, meaning that death is inevitable for all, and can at best be postponed until old age.
Young Pretender a name for Charles Edward Stuart (1720–80), as son of the Old Pretender; the name is first recorded from 1745 (the year of the second Jacobite Rising).
young saint, old devil proverbial saying, early 15th century; meaning that unnaturally good and moral behaviour at an early age is likely to change in later life.
Young Turk a member of a revolutionary party in the Ottoman Empire who carried out the revolution of 1908 and deposed the sultan Abdul Hamid II; in extended usage, a young person eager for radical change to the established order.

See also angry young man, those whom the gods love die young, the good die young, hang a thief when he's young, you cannot put an old head on young shoulders.