Cassia cinnamon from China is sometimes referred to as “tung hing”. Is this Mandarin for cassia cinnamon or does it refer to a region in China?
Do you think it is possible to find the Chinese characters for ‘tung hing’? It doesn’t feel piyin to me.
Well, here’s an entire Mandarin article on the subject
I can’t find mention of Tung Hing inside there at all
Yes, the actual Chinese characters will help. This sounds Cantonese to me, though I’m not sure without seeing the characters. ‘Tung’ is probably 東, which means ‘east’.
According to MBDG Cantonese, Tung Hing is 同兴, a region in Zhiejiang (浙江), but I am not quite sure this is correct. I pop down by a Chinese medicial herb shop and ask on my way to the mall later.
I don’t have the characters, I’ve just seen it in pinyin. Here is what wikisays:
Maybe the Chinese wiki entry will refer to it.
In Wade-Giles romanization this would be t’ung hsing; in pinyin it’d be tongxing.
The Chinese proper name is 肉桂, or roggui. Can’t find the relationship to Ting Hui. It’s very likely to be a Cantonese name, but not sure if MBDG is translating it right.
This is the character conversion:
Tung Hing = 東興 (traditional) = 东兴 (simplified) = dong xing
As the OP had guessed, Dongxing is a city in Guangxi province, in China, not the name of cinnamon in Chinese. Cinnamon in Chinese is 肉桂 (as CrazyChop mentions), although I have also found 桂桂 (guigui).
The relationship comes from the fact that a lot of cinnamon is produced in that area, near the Vietnamese border, so Dongxing cinnamon seems to have become a staple name for the spice in China.
By the way, regarding the romanization method. It seems to me to be the Hong Kong Government Cantonese romanization (Hong Kong Government Cantonese Romanisation - Wikipedia), which is a hell of a system without many clear rules and that competes with many other systems… my guess for this is just that there is a street in HK called Tung Hing, so if anybody has a better explanation…
Or else it was just made up by Sum Yung Gai . . .
The system is in very common use in Hong Kong. The problem with this system is that many distinct consonants and vowels are all mapped to the same spelling, so it’s not going to work for someone trying to learn the language. But it seems to be adequate for romanizing names for the benefit of non-Chinese readers. The rules may not be clearly written down, but there’s definitely method to the madness, and most people can easily tell if something is not romanized using the normal convention.
And that is a perfect definition of Hong Kong 
You guys rock! Xie xie nimen.