root cellar vs undercroft

root cellar

noun
  • A structure built underground or partially underground and used to store vegetables, fruits, and nuts or other foods. 

verb
  • To cellar (food) in a root cellar. 

undercroft

noun
  • A cellar or vaulted storage room. 

  • A ground-level car park that occupies the base of a building. 

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