eccentricity vs irregularity

eccentricity

noun
  • The quality of being eccentric or odd; any eccentric behaviour. 

  • The ratio, constant for any particular conic section, of the distance of a point from the focus to its distance from the directrix. 

  • The eccentricity of the conic section (usually an ellipse) defined by the orbit of a given object around a reference object (such as that of a planet around the sun). 

irregularity

noun
  • The state or condition of being irregular, or the extent to which something is irregular. 

  • A violation of rules. 

  • An object or event that is not regular or ordinary. 

  • An instance of being irregular. 

  • Irregular bowel movement (e.g. diarrhea or constipation). 

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