It's a Chinglish. In Chinese Niu means cow,which also means that someone is very capable. Bi (pronunciation Bee), which is used to refer a person rudely. 中式英语词汇。在汉语中，“Niu”的意思是牛，也含有某人很厉害很有能力的意思。“Bi”（发Bee音）是对人的粗鲁称呼。
