kindergarten vs seedbed

kindergarten

noun
  • An educational institution for young children, usually between ages 4 and 6; nursery school. 

  • The elementary school grade before first grade. 

  • The two levels between nursery and prep; the second and third years of preschool. 

seedbed

noun
  • A place conducive to development and attainment. 

  • Ground prepared for the planting of seeds. 

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