Tanned, dried, scraped elephant skin. While quite tough, it is a poor insulator.
The following animals provide elephant leather.
Elephant leather is the tied 6th most protective textile against sharp and blunt, and tied 3rd against heat. While it is not a good insulator, it is a very good candidate for dusters and protective clothing in the early game in biomes that don't experience temperature extremes. However it should be replaced by better materials such as Devilstrand in the mid-game, with dusters receiving priority. As it provides enough sharp protection for even pants and button-down shirts to have a chance to stop attacks, it can be valuable to transition to using elephant leather for those items to save limited stocks of better materials for dusters where they will have more impact while still providing some chance to deflect a blow after AP. The exceptional amount of leather that a single elephant provides mean that as single manhunter event can produce a lot of leather for this purpose as well.
For use in furniture, it has a middle-of-the-road beauty factor, but its eventual redundancy as clothing and the demand for more beatiful textiles like Thrumbofur in other roles makes it a decent choice for improving furniture beauty once the colony has transitioned to more protective textiles.