noun
Derogatory term for a young, inexperienced person, often a child or apprentice, implying cheekiness or lack of skill. Similar to calling someone a 'young punk' or 'snot-nosed kid'.
あの小僧っ子がまた生意気な口をきいた。
That brat talked back again.
まだ小僧っ子のくせに、一人前のつもりか。
You're still a greenhorn, yet you think you're a full-fledged adult?
小僧 is a more common and slightly less emphatic derogatory term for a young boy or apprentice. 小僧っ子 adds the diminutive 子 and the emphatic っ, making it more contemptuous and colloquial.
青二才 also means 'greenhorn' or 'young punk', but is more literary and less common in modern casual speech. 小僧っ子 is more colloquial and directly insulting.
Derived from 小僧 (こぞう, 'youngster' or 'apprentice') with the diminutive suffix 子 (こ) and an emphatic geminate っ, yielding a more contemptuous and colloquial form. The exact historical derivation is uncertain, but the components are transparent.