attic vs undercroft

attic

noun
  • A person's head or brain. 

  • The space, often unfinished and with sloped walls, directly below the roof in the uppermost part of a house or other building, generally used for storage or habitation. 

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 attic and undercroft occurred in a corpus of books? (source: Google Ngram Viewer )