Coconut : Coir :: Flax : ? Complete the analogy.

Coir is the coarse fibre stripped from the husk of a coconut, and linen is the cloth got from the fibre of the flax plant, so each pair joins a plant to the material it yields. Jute comes from the jute plant, silk from the silkworm, and denim is a heavy cloth woven from cotton — none of the three comes from flax.