give someone the boot vs unhire

give someone the boot

verb
  • (idiomatic, Britain, informal) To fire, sack, or eject someone. 

  • Used other than figuratively or idiomatically: see give, the, boot. 

unhire

verb
  • To fire; to terminate the employment of (somebody previously hired). 

How often have the words give someone the boot and unhire occurred in a corpus of books? (source: Google Ngram Viewer )