Cotton, linen, silk, or manmade material treated withlinseed oil, vanish for waterproofing. Used for rainwear.
an oiled waterproof cloth used for coverings and garments.
Oilskin referred originally to a type of fabric - canvas with, literally, a skin of oil applied to it as waterproofing. These days, oilskins or oilies means the foul-weather gear worn by sailors, made of modern and often quite advanced fabrics.