The term LINEN FIBER SOURCE is referring to the plant FLAX, which is a four letter word. FLAX is an annual herbaceous plant that is cultivated for its fibers and seeds. The fibers of the FLAX plant are used to make linen fabric, which is one of the oldest fabrics in the world. FLAX is also used to make paper, twine, and rope. The seeds of the FLAX plant are used to make linseed oil, which is used in paints, varnishes, and soaps.