cotton wool vs silk

cotton wool

noun
  • Raw fibers of cotton before being processed. 

  • Soft, absorbent cotton for medical or cosmetic use, protective padding, etc. 

silk

noun
  • A fine, soft cloth woven from silk fibers. 

  • Anything which resembles silk, such as the filiform styles of the female flower of maize, or the seed covering of bombaxes. 

  • A pair of long silk sheets suspended in the air on which a performer performs tricks. 

  • A fine fiber excreted by the silkworm or other arthropod (such as a spider). 

  • The gown worn by a Senior (i.e. Queen's/King's) Counsel. 

  • A Queen's Counsel, King's Counsel or Senior Counsel. 

  • The garments worn by a jockey displaying the colors of the horse's owner. 

verb
  • To remove the silk from (corn). 

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