pacifier vs sleeping pill

pacifier

noun
  • A rubber or plastic device imitating a nipple that goes into a baby’s mouth, used to calm and quiet the baby. 

  • Someone or something that pacifies. 

sleeping pill

noun
  • A pill or tablet having a soporific effect. 

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