Bolshevik vs social-democrat

Bolshevik

noun
  • A Russian communist revolutionary, member of the Bolshevik Party in the 1917 Communist Revolution of Russia. 

  • A member of the Communist Party that ruled the Russian Soviet Federative Socialist Republic and the Union of Soviet Socialist Republics. 

social-democrat

How often have the words Bolshevik and social-democrat occurred in a corpus of books? (source: Google Ngram Viewer )