The Chinese term "Wo Nu" (倭奴), literary meaning "Japanese Slaves", was used to refer to the Japanese Nation before Yuan Dynasty, and had grown into an equivalent of "Wo Kou", or "Japanese pirates", by the time of Yuan and Ming Dynasties. However, the term became more complicated in the context of Macao during Ming Dynasty: it included some half-merchant-half-pirate "Wo Kou" and more Japanese Christian exiles fleeing the crackdown of Catholicism back home; in addition, there were large numbers of slaves in the true sense of the word, purchased by the Portuguese from Kyushu, Japan. It is this last group of "Wo Nu" that draws the attention of the present essay, which seeks to clarify the meaning of the term by using Chinese, Japanese and Western materials and to justify the Ming Cantonese Government's judgments of the nature of the Wo Nu in Macao and its policies toward them.