heed vs vacuity

heed

verb
  • To mind; to regard with care; to take notice of; to attend to; to observe. 

noun
  • Careful attention. 

vacuity

noun
  • Idleness; listlessness. 

  • Emptiness. 

  • Physical emptiness, an absence of matter; vacuum. 

  • An empty or inane remark or thing. 

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