Derivation(?) of "Snob" and "Cad."

I am informed by my son, who goeth to a Latin school, that *Snob* (which is a word he often useth) cometh of two Latin words; to wit, "*sine obolo*"—as who should say, "one that hath not a cross to bless himself." He saith, that the man behind the omnibus is called "*Cad*," "a *non cadendo*." Your humble servant,