Why is the old name of Taiwan Province Province for mainlanders "Tangshan people"?

Most compatriots in Taiwan Province Province immigrated from Fujian, and a large part of local residents in Fujian immigrated from the Central Plains during the Tang Dynasty. For the remote Fujian province at that time, "Tang people" naturally became the appellation of Central Plains people. Later, Taiwan Province Province called the mainland "Tang people", called the mainland "Tangshan" and called his surname ancestors "Tangshan ancestors", which is the continuation of this historical title.