unprolific vs vain

unprolific

adj
  • Not prolific. 

vain

adj
  • Having no real substance, value, or importance; empty; void; worthless; unsatisfying. 

  • Overly proud of oneself, especially concerning appearance; having a high opinion of one's own accomplishments with slight reason. 

  • Showy; ostentatious. 

  • Effecting no purpose; pointless, futile. 

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