Back as early as 16th Century Wales, legend has it that flannel or a flannel-like material was created from wool. The main purpose of the fabric was to produce warm clothing in a notoriously cold climate. At various stages, flannel became a popular material for bedding, blankets, and sleepwear as well.
Today's flannel can be made of wool, cotton, or synthetic fiber but the purpose has remained the same. Flannel clothing is still a popular choice thanks to its combination of durability, softness, comfort, and warmth. This is why it has been so strongly adopted by hikers, backpackers, and the outdoorsy.