oftentimes vs rarely

oftentimes

adv
  • (elsewhere, archaic) Frequently; often 

rarely

adv
  • Not occurring at a regular interval; seldom; not often. 

  • To a rare degree; very. 

  • Unusually well; excellently. 

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