security blanket vs subtraction

security blanket

noun
  • A blanket that one uses to have a secure feeling or reduced anxiety, usually in the early years of life. 

  • Any object one uses to have a sense of security or reduced anxiety. 

subtraction

noun
  • The process of subtracting a number from another. 

  • A calculation involving subtracting. 

  • The removal of something. 

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