cohabit vs do it

cohabit

verb
  • To live together with someone else, especially in a romantic and sexual relationship but without being married. 

  • To coexist in common environs with. 

do it

verb
  • To have sex; make it. 

  • To urinate. 

  • To be appealing or suitable. 

  • Used other than figuratively or idiomatically: see do, it. 

  • To do something exceptionally foolish or unacceptable. 

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