Since we are talking about "Fearnought" rather than Dsel's Fearnaught, may I mention that there are at least two references in Patrick O'Brian's Aubrey/Maturin novels. One definition of the cloth sense is:
fearnought A stout woolen cloth used as clothing in cold weather. Also, a thick felt used to cover the outside door of a powder MAGAZINE, portholes, and HATCHWAYS during battle. Also called “dreadnought screen.”
When our hero has a cold he is offered "fearnought draught" which has the interesting characteristic that it has to be drunk in twos, "or the first glass is mortal"!