Coir

Coir (pronounced COY-er) comes from coconuts. It's what makes up the fibrous husks of the inner shell of the coconut and is used for all sorts of products, including rugs, ropes, brushes, and even upholstery stuffing. You're probably most familiar with it as those stiff, scratchy doormats and the fibrous liners used in hanging baskets. Coir is very rot-resistant, making it perfect for outdoor products. It is also becoming increasingly popular as a potting mix and organic soil amendment.

Source : https://www.thespruce.com/what-is-coir-1403141