Boy
Boy or lad or kid would fit.
fry
cub
Boy or kid
The three-letter word that means "young louse" is "nit." Perhaps the "r" is incorrect.
Lad
kid. the child of a goat
A... Toddler Kid Child
Well, "man" and "boy" both have three letters, but you could also use "guy".
boy, lad
3 letter word for old oldsmobile