doorstep vs gradation

doorstep

noun
  • One's immediate neighbourhood or locality. 

  • An outside step leading up to the door of a building, usually a home. 

  • A thick slice, especially of bread. 

verb
  • To visit one household after another to solicit sales, charitable donations, political support, etc. 

  • To corner somebody for an unexpected interview. 

gradation

noun
  • Any degree or relative position in an order or series. 

  • A calibration marking. 

  • A passing by small degrees from one tone or shade, as of color, to another. 

  • A diatonic succession of chords. 

  • Apophony. 

  • A gradual change within one parameter, or an overlapping of two blocks of sound. 

  • A sequence of gradual, successive stages; a systematic progression. 

  • The act of gradating or arranging in grades. 

verb
  • To form with gradations. 

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