get behind vs substantiate

get behind

verb
  • To appreciate, to enjoy. 

  • To support, to cheer on. 

  • To have a trip or any pleasurable experience with drugs. 

  • To come to believe something; to change one's mind into a new position. 

  • Used other than figuratively or idiomatically: see get, behind. 

substantiate

verb
  • To give material form or substance to something; to embody; to record in documents 

  • To verify something by supplying evidence; to authenticate or corroborate 

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