priority vs unimportance

priority

noun
  • A goal of a person or an organisation. 

  • A superior claim to use by virtue of being validly published at an earlier date. 

  • The quality of being earlier or coming first compared to another thing; the state of being prior. 

  • right of way; The right to pass (an intersection) before other road users 

  • An item's relative importance. 

unimportance

noun
  • Lack of importance. 

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