anagram vs riddle

anagram

noun
  • A word or phrase that is created by rearranging the letters of another word or phrase. 

verb
  • To form anagrams. 

riddle

noun
  • An ancient verbal, poetic, or literary form, in which, rather than a rhyme scheme, there are parallel opposing expressions with a hidden meaning. 

  • A board with a row of pins, set zigzag, between which wire is drawn to straighten it. 

  • A verbal puzzle, mystery, or other problem of an intellectual nature. 

  • A sieve with coarse meshes, usually of wire, for separating coarser materials from finer, as chaff from grain, cinders from ashes, or gravel from sand. 

  • One of the pair of curtains enclosing an altar on the north and south. 

verb
  • To fill with holes like a riddle. 

  • To speak ambiguously or enigmatically. 

  • To fill or spread throughout; to pervade. 

  • To put something through a riddle or sieve; to sieve; to sift. 

  • To solve, answer, or explicate a riddle or question. 

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