When I was a kid and collected stamps, I remember being struck by the exotic name “Tannu Tuva” as well as the exotic stamps produced under that name (as that article says, “these exotic stamps were popular with young collectors during the middle of the twentieth century”). I’ve been going through some old files and I found a sheet headed “From Alt.culture.tuva FAQ Version 1.41” addressing the question of how that “Tannu” got there, which I apparently printed out in 1999; I was afraid I’d have to copy it out to post it, but it turns out a slightly more recent (2001) version of the FAQ is online here, so I can just copy and paste:
12: How did the “Tannu” get into “Tannu Tuva”?
A: Several Mongolians and the band Ozum were asked about the word “Tannu”; they did not know the word or its source. Mongolians and Tuvans both answered “it may not be Tannu, it must be Tangdy”. They opined that it must be a Tuvan term; it is certainly not Mongolian. Their guess is that Tangdy is the word printed on some maps as “Tannu-Ola” (in Tuvan dictionaries this appears as “Tangdy cyny” or “Tangdy-Uula”). As you may know, tangdy (ta”ng”dy) means “high mountain” or “taiga surrounded by high mountain” in Tuvan.
Here is some supporting information, mainly from a book by S. A. Shoizhelov (Matson), Tuvinskaya Noonday Republican [copying error for “Narodnaya Respublika”], Moscow 1930. (Written in Oct. 1929).
Tuva was indeed called “Tang-nu Wulianghai”. The Czarist Russians called Tuva “Uryanhai”. P. 29-30 of the above mentioned book talks about a “Russo-Uryanhai regional meeting”, in which, of course, a resolution was passed. This meeting was after, and supposedly in response to, the February Revolution of 1917. The meeting was held in Byelotsarsk, and was convened by the Immigrants’ Administration (Pereselencheskogo Upravleniya). Kyzyl was called Byelotsarsk (“White Tsar Town”) from 1914 until 1918, then was known as Khem-Beldyr until 1926, and has been called Kyzyl since then.
Article One of this resolution refers to “Tannu-Uryanh[a]i”, obviously a corruption or Russianization of “Tang-nu Wulianghai”.
Once the Russians decided to call the Tuvans “Tuvans” and not “Uryanhais”, then it was a natural step for them to quit calling the place “Tannu-Uryanhai” and call it “Tannu-Tuva” instead.
In his discussion of the first meeting of the Party in Tuva, Natsov refers to the “Tannu-Tuva”, but then afterwards it is always simply “Tuva”. At the founding of the nominally independent state, it was called the Tannu-Tuvan People’s Republic, but that soon afterward, in just a few years, the “Tannu” was dropped.
As we all know, the first Tuvan postage stamps, issued in 1926, have “Ta Ty” for Tangdy Tyva on them. The next issue, from 1927, has just “Tyva”.
Baylan Cannol, a systems engineer from Teeli, Tuva, confirms that yes, “Tannu” is a corrupted form of “Tangdy”. During the era of the Tannu-Tyva Arat Republic (TAR) there was a division of Tuvan people into several parts, depending on where the Tuvan lived. The distinct divisions included the “Tangdy Tyvazy” (those living in Tuva) and the “Kalga Tyvazy” (Tuvans living in Mongolia). In those times, Tuvans living in different areas had more relations with each other as one people. Since the union of Tannu Tuva with Russia, Tannu Tuva has almost forgotten the Kalga Tyvazy and other groups.
Baylan also confirms that ‘Tangdy Tyva’ doesn’t correspond with ‘Tangdy Uula’, and ‘Tangdy Uula’ is just a mountain in the south. The word “tangdy” means the same as the word “taiga” (subarctic coniferous forests, which are mainly in Tannu Tuva, not in Mongolia, China etc.).
Of course, I have no way of knowing if that’s all true, and any updates, addenda, or random comments are, as always, welcome.