second childhood vs superannuation

second childhood

noun
  • The period or state of cognitive decline of an elderly person, characterized by childlike judgment and behavior. 

  • A childlike state in any adult, resulting from mental illness, trauma, or other conditions. 

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 second childhood and superannuation occurred in a corpus of books? (source: Google Ngram Viewer )