cold frame vs glasshouse

cold frame

noun
  • A transparent-roofed enclosure, built low to the ground, used to protect plants from cold weather. 

glasshouse

noun
  • A greenhouse, especially one for commercial use. 

  • A building where glass or glassware is manufactured. 

  • A military prison. 

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