backdate vs usher

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. 

usher

verb
  • To precede; to act as a forerunner or herald. 

  • To lead or guide somewhere. 

  • To accompany or escort (someone). 

  • To guide people to their seats. 

noun
  • A male escort at a wedding. 

  • A doorkeeper in a courtroom. 

  • A person, in a church, cinema etc., who escorts people to their seats. 

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