Let's meet Xiju
In Ancient Fuzhou Dialect -- Song-Lai(上沙)
According to the Notes of Min and Yue in Sikuquanshu(四庫全書-粵閩巡視紀略), it said, "The islands are called 'Baiquan' (white dog) for they looking like two dogs leaning on waves. It is dangerous to park boats on these islands when typhoon comes." So Xiju was officially called Xi-Quan(西犬) in the dock. For at the Dong-Lai(東沙, today's Dongju) in ancient maps, Xiju was called "Song-Lai" as well.
Annals of Fujian printed during Qing emperor Kangxi years (1661-1722).
Sikuquanshu has very detailed introduction about Matsu islands.
Including features in every island and navigation informatioins.
Xiquan was important in Qing Dynasty's international trade. Foreign ships would stop here in the past. Because there were foreign people (洋人) on this island, it's also called "Bai-Quan-Yang(白犬洋)" . Don-Lai(東沙) was also called Xia-Lai (下沙) for it's lower position in the view from Fuzhou.
Picture from Juguang Township Annals
The origin of Xiju
Dog is not a noble animal in Chinese culture. So Chiang Kai-Shek asked the Matsu Defense Command to changed "Baiquan Township" into "Juguang Township" In 1971, to memorize the historical story of Ju. And Xiju replaced Xiquan to be the official title of this island.
Matsu islands in Ming Dynasty's map.
Don't you think they look like pearls outside the Min River?
Picture from Juguang Township Annals
texture and picture resource from Yamamoto Legion