posset vs underscore

posset

verb
  • To treat with possets; to pamper. 

  • To vomit up curdled milk. 

noun
  • A beverage composed of hot milk curdled by some strong infusion, such as wine. 

  • A baby's vomit, comprising curdled milk. 

underscore

verb
  • To emphasize or draw attention to. 

  • To underline; to mark a line beneath text. 

noun
  • An underline; a line drawn or printed beneath text; the character _. 

  • A piece of background music. 

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