extortionate vs undue

extortionate

adj
  • Greatly exceeding what is moderate or reasonable; exorbitant. 

  • Of, related to, or typifying extortion (“the practice of obtaining money or other property by the use of force or threats”). 

undue

adj
  • Excessive; going beyond that what is natural or sufficient. 

  • That which ought not to be done; illegal; unjustified. 

  • Not owing or payable. 

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