Boy
Lad
Boy or lad or kid would fit.
fry
man
cub
The three-letter word that means "young louse" is "nit." Perhaps the "r" is incorrect.
delivery man
Man (MAN-ager, manager)
A three-letter word for (human) male offspring is "son."
kid. the child of a goat
A... Toddler Kid Child
Old age.