Tannins in tea?

I am a tea enthusiast who runs a small business in Scandinavia. I am often approached by customers on the subject of tannic acid in tea. This myth is being strengthened by numerous web shops stating that their teas are free of tannic acid, implying that other teas are not. I would like to bury this myth once and for all and I am in the process of writing an article in Danish about tannin contra tannic acid in tea. 

Like most tea people I was under the assumption that there is in fact tannin in tea (Proanthocyanidins, a different chemical to tannic acid with a longer carbon chain), however I have tried to research tea tannin but cannot find any documentation that it actually exists in tea. There is no reference to tannin in books on tea chemistry and it is not mentioned on your website either. Is this something you can help me with? 

Does tannin actually exist in tea? If so how and why does it occur? 

Does it have a taste, an odour or colour, and are there any benefits/downsides from this chemical? 

Any ideas on how tannin became tannic acid? 

I have read somewhere that the word tannin is derived from the German “Tanna” meaning oak or pine as in Tannenbaum (Christmas tree). Tannic acid is pressed from the bark and leaves of an oak tree to tan hide. I can’t imagine any cup of tea tanning leather.