retirement vs superannuation

retirement

noun
  • The state of being retired; seclusion. 

  • An act of retiring; withdrawal. 

  • The state of having permanently left one's employment, now especially at reaching pensionable age; the portion of one's life after retiring from one's career. 

  • The act of leaving one's career or employment permanently. 

superannuation

noun
  • The condition or of being superannuated; old age or obsolescence. 

  • A retirement benefit fund, an accumulation of regular deductions from one′s wage or salary while employed and similar regular contributions from the employer, usually administered by an independent entity; a pension. 

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