barter vs hire out

barter

verb
  • To exchange goods or services without involving money. 

noun
  • An exchange of goods or services without the use of money. 

  • The goods or services used in such an exchange. 

hire out

verb
  • To allow others to use temporarily in exchange for money. 

  • To arrange to do work for money. 

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