covert vs incubator

covert

noun
  • A covering. 

  • A disguise. 

  • A feather that covers the bases of flight feathers. 

  • Area of thick undergrowth where animals hide. 

  • A hiding place. 

adj
  • Under coverture. 

  • Secret, surreptitious, concealed. 

incubator

noun
  • 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. 

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

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