Tivish was a plant-based fiber originating on Remus' southern continent, used by the Romulans to make fabric.
Tivish was extremely difficult to correctly process and as a result was very expensive. It was comparable in appearance and feel to silk, and the finest-grade tivish was said by Leonard McCoy to be "so fine, you can have it in your hands and hardly know when you're feeling it."
When the Romulan Star Empire banished Kaveth Ship-Clan from Remus to the colony planets in the 2220s for speaking out against the government, the Kavethssu smuggled out with them the plants from which tivish was made. They spent the next half-century exporting hydroponically grown tivish back to Romulus and Remus, mislabeled as coming from Remus. In the lead-up to the Romulan Civil War of 2276 the Ship-Clans used the proceeds to finance the construction of the starships Tyrava and Kaveth, intent on leaving the Empire to resettle elsewhere. (TOS - Rihannsu novel: The Empty Chair)