Is there much we know about the Tholians?

[Tenacity]

Which doesn't mean it's literally silk. Humans have always applied the name of something familiar to new things that remind them of it.

Or, it's just actual silk.

 

[F. King Daniel]

No clue where it's from (either a licensed novel or some fanfic), but I know I've read somewhere the idea that Tholians originate outside our timeline/universe. I kinda liked that idea, since we meet them near the interphase which links the 23rd century Prime universe with the 22nd century mirror universe, and we see they're involved in the temporal cold war.