sharpen vs taper

sharpen

verb
  • To become sharp. 

  • To make sharp. 

taper

verb
  • To become thinner or narrower at one end. 

  • To diminish gradually. 

  • 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 sharpen and taper occurred in a corpus of books? (source: Google Ngram Viewer )