skittishness vs vacuity

skittishness

noun
  • The property of being skittish. 

vacuity

noun
  • Idleness; listlessness. 

  • Emptiness. 

  • Physical emptiness, an absence of matter; vacuum. 

  • An empty or inane remark or thing. 

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