erratic vs methodical

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. 

methodical

adj
  • In an organized manner; proceeding with regard to method; systematic. 

  • Arranged with regard to method; disposed in a suitable manner, or in a manner to illustrate a subject, or to facilitate practical observation. 

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