incubator vs nest egg

incubator

noun
  • An apparatus used to maintain environmental conditions suitable for the hatching of eggs. 

  • An apparatus used to maintain environmental conditions suitable for a newborn baby. 

  • Any apparatus used to maintain environmental conditions suitable for a reaction. 

  • A place to maintain the culturing of bacteria at a steady temperature. 

  • A support programme for the development of entrepreneurial companies. 

nest egg

noun
  • A natural or artificial egg placed in a bird's nest, to encourage the bird to lay its own eggs there. 

  • An egg squash. 

  • A saving; a reserve of money. 

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