SzeYup (四邑) (sometimes spelled Siyi and variants) refers to the four counties of Xinhui 新會 Taishan 台山, Kaiping 開平 and Enping (恩平) in the Pearl River Delta of southern Guangdong province, China. This is the area marked in Green.
In the 19th century, many people from SzeYup emigrated to Hong Kong, Southeast Asia, Australia, North America and South America. Of the Australian Chinese population from that time until the 1950s, SzeYupnese were the vast majority, along with people from Sanyi and Zhongshan. SzeYupnese generally worked as labourers; Sanyi (南海, 番禺, 顺德) (Area marked in purple) people worked as entrepreneurs; and Zhongshan (中山) people specialized in agriculture.
More information on SzeYup and XinHui can be found here http://legacy1.net/xinhui-county/