lucidity vs readability

lucidity

noun
  • The property of being lucid, lucidness. 

  • The state of being aware that one is dreaming, i.e. being in a lucid dream. 

readability

noun
  • The property of being capable of being read; legibility. 

  • The property of being easy or engaging to read. 

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