I noticed in the Đại Việt Sử Ký Toàn Thư that Đinh Bộ Lĩnh, the founder of the Đinh Dynasty, was from a place called “động Hoa Lư” in what is today Ninh Bình Province. động (峒) is a word which literally means “grotto.” However, it was used by Chinese to refer to areas which were under the control of certain non-Han Chinese peoples.
In his article, “The Zhuang Minority Peoples of the Sino-Vietnamese Frontier in the Song Period” [Journal of Southeast Asian Studies 18.2 (1987), 250-269], Jeffrey G. Barlow notes that this term, động, is a Zhuang term which has the same meaning as the Tai term muang, which refers to a mountain valley and a polity, because individual Tai polities were first formed in separate mountain valleys.
This geographic description certainly fits Hoa Lư. For instance, the Khâm Định Việt Sử Thông Giám Cương Mục has the following to say about Hoa Lư:
“Hoa Lư was in the mountains parts of the two communities of Uy Viễn and Uy Tế in Ninh Bình [Province]. This area has mountain cliffs standing upright in all four directions. In the middle is an area of relatively flat and spacious land. The local people call it Hoa Lư Grotto.” [Tiền Biên 5/24b]
That same text mentions other grottoes during the period of Chinese rule, such as Khuất Lạo Grotto, Dã Năng Grotto, and Hoàng Grotto. The “Lạo” in Khuất Lạo Grotto is a good indication that the people who lived there were Tai speakers [Note: I am using the term “Tai” in the manner in which Western scholars use it, to refer to all of the various peoples who are part of the Tai language family, be they Lao, Zhuang, Black Tai, etc.]. The name, Dã Năng, doesn’t tell us much, but it is clear from the context when it appears in the historical records that this was also an area inhabited by Tai speakers. And finally, Hoàng is a name which the Chinese gave to many Zhuang [See Jeffrey Barlow’s web page on the Zhuang], so it is highly likely that Hoàng Grotto was also an area inhabited by Tai speakers.
So that leaves Hoa Lư Grotto. Hmmm . . . was Đinh Bộ Lĩnh Tai?