rippling vs undulation

rippling

noun
  • A motion or sound that ripples. 

adj
  • Moving in a chaotic, undulating fashion, as in a flow of water or a flag blowing in the wind. 

undulation

noun
  • A wavy appearance or outline; waviness. 

  • An instance or act of undulating. 

  • A wavelike curve; a smooth and regular rise and fall. 

  • A wavelike motion of the air; electromagnetic radiation. 

  • A tremulous tone produced by a peculiar pressure of the finger on a string. 

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