Vercetti is right. It`s Vaffanculo, although like cumare (goumatta) and cafone (gavone) it is slanged (is that a word?) . Italian words are constantly transfered to slang. But, both ways can be used.
Getting back to the original question: There are a few Anglo-Saxonisms in the novel, including the f-word and the s-word and the a-hole word, but Puzo uses them rather sparingly.