customary vs erratic

customary

adj
  • In accordance with, or established by, custom or common usage 

  • Holding or held by custom 

noun
  • A book containing laws and usages, or customs; a custumal. 

erratic

noun
  • A rock moved from one location to another, usually by a glacier. 

  • Anything that has erratic characteristics. 

adj
  • Deviating from normal opinions or actions; eccentric; odd. 

  • Unsteady, random; prone to unexpected changes; not consistent. 

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