retard vs taper

retard

verb
  • To decelerate; to slow down. 

  • To put off; to postpone. 

  • To keep delaying; to continue to hinder; to prevent from progressing. 

noun
  • Retardation; delay. 

  • A slowing down of the tempo; a ritardando. 

  • A person or being who is extremely stupid or slow to learn. 

taper

verb
  • To diminish gradually. 

  • To become thinner or narrower at one end. 

  • To make thinner or narrower at one end. 

  • (of a central bank) To tighten monetary policy. 

adj
  • Tapered; narrowing to a point. 

noun
  • A small light. 

  • A cone-shaped item for stretching the hole for an ear gauge (piercing). 

  • Someone who works with tape or tapes. 

  • A thin stick used for lighting candles, either a wax-coated wick or a slow-burning wooden rod. 

  • One who operates a tape machine. 

  • A slender wax candle. 

  • A tapering form; gradual diminution of thickness and/or cross section in an elongated object. 

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