Tow is the course crushed Flax plant stem. It's crushed to break the fibers free from the stalk. The fibers can then be carded, and spun into linen thread, which can then be woven into linen, or mixed with wool thread to make linsey-woolsey. Back in the 17th, 18th century, and even into the early 19th century Linen, and L-W were the cheap material, the polyester of it's day. Up in value was wool, cotton, and then silk. Cotton was very expensive until the invention of the Cotton Gin to process it. The tow we want for cleaning is coarser, and hasn't been carded very much, if at all. Kind of a brillo pad.
Bill