AB vs Bachelor of Arts

AB

noun
  • A person with this blood type. 

  • A blood type of the ABO system that has both blood antigens and may receive all blood types, and donate to AB. 

Bachelor of Arts

noun
  • A collegiate degree, usually involving three to four years of study (about 120 semester hours) in liberal arts. 

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