backdate vs lead up to

backdate

verb
  • To give or assign a date to a document that is earlier than the current or true date. 

noun
  • An assigned date that is earlier than the current or true date. 

lead up to

verb
  • To precede in time. 

  • To set in motion; to act as a causal or preparatory event or sequence of events. 

  • To follow or mark a path toward. 

How often have the words backdate and lead up to occurred in a corpus of books? (source: Google Ngram Viewer )