anomaly vs anybody's guess

anomaly

noun
  • Something or someone that is strange or unusual. 

  • Any of various angular distances. 

  • A defect or malformation. 

  • A failure of a classical symmetry due to quantum corrections. 

  • Any event or measurement that is out of the ordinary regardless of whether it is exceptional or not. 

  • A deviation from a rule or from what is regarded as normal; an outlier. 

anybody's guess

noun
  • Synonym of anyone's guess 

How often have the words anomaly and anybody's guess occurred in a corpus of books? (source: Google Ngram Viewer )