describe vs spell out

describe

verb
  • To represent in words. 

  • To give rise to a geometrical structure. 

  • To introduce a new taxon to science by explaining its characteristics and particularly how it differs from other taxa. 

  • To represent by drawing; to draw a plan of; to delineate; to trace or mark out. 

spell out

verb
  • To form (a word) from letters; say the letters in a word. 

  • To explain in clear and simple terms; to be explicit. 

  • To replace an acronym with its expansion. 

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