oilskin vs topcoat

oilskin

noun
  • A raincoat made from cotton fabric treated with oil and pigment to make it waterproof. 

  • Cloth made from cotton and treated with oil and pigment to make it waterproof. 

  • Foul-weather gear worn by sailors, whether of natural or synthetic materials. 

topcoat

noun
  • A layer of paint or varnish etc. applied after the undercoat. 

  • A light overcoat. 

verb
  • To apply a topcoat to. 

How often have the words oilskin and topcoat occurred in a corpus of books? (source: Google Ngram Viewer )