Silk Noil is the short bits that are left from the silk cocoon after the finest silk has been reeled off. Some say it is short because the caterpillar chewed a hole to emerge...and that may be the case with some Tussah silks. Silk noil can be spun into a very slubby yarn. The fabric woven from silk noil yarn used to be called "raw silk." In the 1960's, my mother would get all excited about owning a suit made from "raw silk." It was pretty fabric: tweedy but lustrous.
I have been using silk noil for years as an additive for wild batts. I use it to put soft, contrasting color slubby bits in wool yarn. This year, for the first time, I will have a limited supply of dyed s ilk noil for sale at Shepherd's Harvest.