I have since discovered in a Dutch on-line dictionary that tibet is made from Tibetan sheep rather than goats or antelopes in the Himalayas. It seems the sheep have an undercoat of fine wool as well as the coarser, hairier outer coat, according to the Wikipedia pages on these sheep.

Good to hear of 'thibet'. Which OED did you use? I have the Concise version, the Mac OS version which I thought was quite extensive, Oxford Reference Online and Oxford Art/Grove Art Online, Oxford Dictionaries Online but could not find tibet (fabric).

Yes, 'stuff' is an old term for fabric. Incidentally, 'stof' is one of the Dutch terms for fabric and still used today.

And indeed, there are many varieties on the same terms and not just for textiles, which is vaguely reassuring.

The search goes on...