Confederacy vs Confederate States of America

Confederacy

name
  • The Confederate States of America, the collection of American states that seceded from the United States in 1860–61, and fought against the Union in the American Civil War. 

Confederate States of America

name
  • An unrecognized nation existing from 1861–1865, consisting of the eleven Southern states who sought independence from the United States of America over the issue of slavery. 

How often have the words Confederacy and Confederate States of America occurred in a corpus of books? (source: Google Ngram Viewer )