retardation vs worm in the apple

retardation

noun
  • That which retards; an obstacle; an obstruction. 

  • The distance by which one wave is behind another. 

  • The extent to which anything is retarded; the result of any retarding or delay; mental, social, or physical slowness. 

  • Deceleration; reduction in the magnitude of velocity. 

  • Extreme stupidity. 

  • A decrease in the speed of telegraph signalling. 

  • A suspension which resolves upwards. 

  • The act of diminishing the rate of speed. 

worm in the apple

noun
  • A serious flaw in something otherwise good; a problem that ruins everything else. 

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