attenuate vs phase down

attenuate

verb
  • To reduce in size, force, value, amount, or degree. 

  • To reduce the amplitude of an electrical, radio, or optical signal. 

  • To weaken. 

  • To become thin or fine; to grow less. 

  • To rarefy. 

  • (of a beer) To become less dense as a result of the conversion of sugar to alcohol. 

  • To reduce the virulence of a bacterium or virus. 

  • To make thinner, as by physically reshaping, starving, or decaying. 

adj
  • Gradually tapering into a petiole-like extension toward the base. 

phase down

verb
  • To gradually reduce the size or scale of 

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