One theory has it this way: During the Japanese occupation period in Taiwan, some Taiwanese went to the mainland to do business. Because Taiwan's shape is similar to that of a sweet yam, they called themselves "yams."
台灣日據時代，有一些台灣人到大陸去作生意，為了方便，便以台灣地形像蕃薯為由，自稱為「蕃薯仔」。