cotton wool vs wool

cotton wool

noun
  • Raw fibers of cotton before being processed. 

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

wool

noun
  • Yarn, including that made from synthetic fibers. 

  • Anything with a texture like that of wool. 

  • The hair of the sheep, llama and some other ruminants. 

  • A cloth or yarn made from the wool of sheep. 

  • A fine fiber obtained from the leaves of certain trees, such as firs and pines. 

  • A resident of a satellite town outside Liverpool, such as St Helens or Warrington. See also Yonner. 

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