erratic vs on the wrong track

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. 

on the wrong track

prep
  • using the wrong general approach to a particular task or problem; pursuing something in an unpromising way 

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